diff --git a/src/admin/pages/OfferDetail.tsx b/src/admin/pages/OfferDetail.tsx
index 967c6b9..d53ee24 100644
--- a/src/admin/pages/OfferDetail.tsx
+++ b/src/admin/pages/OfferDetail.tsx
@@ -678,7 +678,7 @@ export default function OfferDetail() {
           }
         }
         if (!isEdit && result.data?.id) {
-          queryClient.invalidateQueries({ queryKey: ["offers", "list"] });
+          queryClient.invalidateQueries({ queryKey: ["offers"] });
           queryClient.invalidateQueries({ queryKey: ["orders"] });
           queryClient.invalidateQueries({ queryKey: ["projects"] });
           queryClient.invalidateQueries({ queryKey: ["invoices"] });
@@ -690,7 +690,7 @@ export default function OfferDetail() {
             items,
             sections,
           });
-          queryClient.invalidateQueries({ queryKey: ["offers", "list"] });
+          queryClient.invalidateQueries({ queryKey: ["offers"] });
           queryClient.invalidateQueries({ queryKey: ["orders"] });
           queryClient.invalidateQueries({ queryKey: ["projects"] });
           queryClient.invalidateQueries({ queryKey: ["invoices"] });
@@ -736,7 +736,7 @@ export default function OfferDetail() {
       if (result.success) {
         setShowOrderModal(false);
         alert.success(result.message || "Objednávka byla vytvořena");
-        await queryClient.invalidateQueries({ queryKey: ["offers", "list"] });
+        await queryClient.invalidateQueries({ queryKey: ["offers"] });
         await queryClient.invalidateQueries({ queryKey: ["orders"] });
         await queryClient.invalidateQueries({ queryKey: ["projects"] });
         await queryClient.invalidateQueries({ queryKey: ["invoices"] });
@@ -762,7 +762,7 @@ export default function OfferDetail() {
         setInvalidateConfirm(false);
         setOfferStatus("invalidated");
         alert.success(result.message || "Nabídka byla zneplatněna");
-        queryClient.invalidateQueries({ queryKey: ["offers", "list"] });
+        queryClient.invalidateQueries({ queryKey: ["offers"] });
         queryClient.invalidateQueries({ queryKey: ["orders"] });
         queryClient.invalidateQueries({ queryKey: ["projects"] });
         queryClient.invalidateQueries({ queryKey: ["invoices"] });
@@ -789,7 +789,7 @@ export default function OfferDetail() {
         deletingRef.current = true;
         queryClient.removeQueries({ queryKey: ["offers", id] });
         alert.success(result.message || "Nabídka byla smazána");
-        await queryClient.invalidateQueries({ queryKey: ["offers", "list"] });
+        await queryClient.invalidateQueries({ queryKey: ["offers"] });
         await queryClient.invalidateQueries({ queryKey: ["orders"] });
         await queryClient.invalidateQueries({ queryKey: ["projects"] });
         await queryClient.invalidateQueries({ queryKey: ["invoices"] });
diff --git a/src/routes/admin/attendance.ts b/src/routes/admin/attendance.ts
index 5a0d7b1..9eb6de7 100644
--- a/src/routes/admin/attendance.ts
+++ b/src/routes/admin/attendance.ts
@@ -185,7 +185,7 @@ export default async function attendanceRoutes(
         return error(reply, "Nedostatečná oprávnění", 403);
       }
       const attendanceId = Number(query.attendance_id);
-      if (!attendanceId) return error(reply, "Missing attendance_id", 400);
+      if (!attendanceId) return error(reply, "Chybí attendance_id", 400);
       const data = await attendanceService.getProjectLogs(attendanceId);
       return reply.send({ success: true, data });
     }
@@ -193,7 +193,7 @@ export default async function attendanceRoutes(
     // --- action=location: single record with GPS data ---
     if (action === "location") {
       const id = Number(query.id);
-      if (!id) return error(reply, "Missing id", 400);
+      if (!id) return error(reply, "Chybí id záznamu", 400);
       const record = await attendanceService.getLocationRecord(id);
       if (!record) return error(reply, "Záznam nenalezen", 404);
       const isAdmin = authData.permissions.includes("attendance.manage");
diff --git a/src/routes/admin/audit-log.ts b/src/routes/admin/audit-log.ts
index fbd9e0c..1550ef9 100644
--- a/src/routes/admin/audit-log.ts
+++ b/src/routes/admin/audit-log.ts
@@ -12,12 +12,10 @@ import { parseBody } from "../../schemas/common";
 // forensic history.
 const DELETE_ALL_CONFIRM = "DELETE_ALL_AUDIT" as const;
 
-const AuditCleanupSchema = z
-  .object({
-    days: z.number().int().nonnegative().optional(),
-    confirm: z.string().optional(),
-  })
-  .strict();
+const AuditCleanupSchema = z.strictObject({
+  days: z.number().int().nonnegative().optional(),
+  confirm: z.string().optional(),
+});
 
 export default async function auditLogRoutes(
   fastify: FastifyInstance,
diff --git a/src/routes/admin/project-files.ts b/src/routes/admin/project-files.ts
index dd6f0cb..18609fc 100644
--- a/src/routes/admin/project-files.ts
+++ b/src/routes/admin/project-files.ts
@@ -58,7 +58,7 @@ export default async function projectFilesRoutes(
       const { project_id: projectIdStr, path: subPath = "" } = parsedQuery.data;
       const projectId = Number(projectIdStr);
       const project = await getProjectForFiles(projectId);
-      if (!project) return error(reply, "Projekt nebyl nalezen", 404);
+      if (!project) return error(reply, "Projekt nenalezen", 404);
 
       if (!fm.isConfigured()) {
         return error(reply, "Souborový systém není nakonfigurován", 500);
@@ -70,7 +70,7 @@ export default async function projectFilesRoutes(
           return error(reply, "Projekt nemá číslo projektu");
 
         const result = fm.downloadFile(project.project_number, subPath);
-        if (!result) return error(reply, "Soubor nebyl nalezen", 404);
+        if (!result) return error(reply, "Soubor nenalezen", 404);
 
         const stream = fs.createReadStream(result.filePath);
         const encodedName = encodeURIComponent(result.fileName);
@@ -89,7 +89,7 @@ export default async function projectFilesRoutes(
 
       const result = fm.listFiles(project.project_number, subPath);
       if (result === null) {
-        return error(reply, "Složka nebyla nalezena", 404);
+        return error(reply, "Složka nenalezena", 404);
       }
 
       return success(reply, {
@@ -109,7 +109,7 @@ export default async function projectFilesRoutes(
       if ("error" in parsedQuery) return error(reply, parsedQuery.error, 400);
       const projectId = Number(parsedQuery.data.project_id);
       const project = await getProjectForFiles(projectId);
-      if (!project) return error(reply, "Projekt nebyl nalezen", 404);
+      if (!project) return error(reply, "Projekt nenalezen", 404);
       if (!project.project_number)
         return error(reply, "Projekt nemá číslo projektu");
 
@@ -162,7 +162,7 @@ export default async function projectFilesRoutes(
       if ("error" in parsedQuery) return error(reply, parsedQuery.error, 400);
       const projectId = Number(parsedQuery.data.project_id);
       const project = await getProjectForFiles(projectId);
-      if (!project) return error(reply, "Projekt nebyl nalezen", 404);
+      if (!project) return error(reply, "Projekt nenalezen", 404);
       if (!project.project_number)
         return error(reply, "Projekt nemá číslo projektu");
 
@@ -225,7 +225,7 @@ export default async function projectFilesRoutes(
       if ("error" in parsedQuery) return error(reply, parsedQuery.error, 400);
       const projectId = Number(parsedQuery.data.project_id);
       const project = await getProjectForFiles(projectId);
-      if (!project) return error(reply, "Projekt nebyl nalezen", 404);
+      if (!project) return error(reply, "Projekt nenalezen", 404);
       if (!project.project_number)
         return error(reply, "Projekt nemá číslo projektu");
 
@@ -267,7 +267,7 @@ export default async function projectFilesRoutes(
       if ("error" in parsedQuery) return error(reply, parsedQuery.error, 400);
       const projectId = Number(parsedQuery.data.project_id);
       const project = await getProjectForFiles(projectId);
-      if (!project) return error(reply, "Projekt nebyl nalezen", 404);
+      if (!project) return error(reply, "Projekt nenalezen", 404);
       if (!project.project_number)
         return error(reply, "Projekt nemá číslo projektu");
 
diff --git a/src/routes/admin/sessions.ts b/src/routes/admin/sessions.ts
index 4fa63b8..8adec12 100644
--- a/src/routes/admin/sessions.ts
+++ b/src/routes/admin/sessions.ts
@@ -1,7 +1,7 @@
 import { FastifyInstance } from "fastify";
 import prisma from "../../config/database";
 import { requireAuth } from "../../middleware/auth";
-import { success, error } from "../../utils/response";
+import { success, error, parseId } from "../../utils/response";
 import { hashToken } from "../../services/auth";
 
 /** Parse user-agent string into browser, OS, and device icon */
@@ -81,8 +81,8 @@ export default async function sessionsRoutes(
     "/:id",
     { preHandler: requireAuth },
     async (request, reply) => {
-      const id = parseInt(request.params.id, 10);
-      if (Number.isNaN(id)) return error(reply, "Neplatné ID relace", 400);
+      const id = parseId((request.params as any).id, reply);
+      if (id === null) return;
       const authData = request.authData!;
 
       const session = await prisma.refresh_tokens.findFirst({
diff --git a/src/routes/admin/trips.ts b/src/routes/admin/trips.ts
index a92cab5..74eb4d5 100644
--- a/src/routes/admin/trips.ts
+++ b/src/routes/admin/trips.ts
@@ -2,7 +2,7 @@ import { FastifyInstance } from "fastify";
 import prisma from "../../config/database";
 import { requireAuth, requirePermission } from "../../middleware/auth";
 import { logAudit } from "../../services/audit";
-import { success, error } from "../../utils/response";
+import { success, error, parseId } from "../../utils/response";
 import { parsePagination, buildPaginationMeta } from "../../utils/pagination";
 import { parseBody } from "../../schemas/common";
 import { CreateTripSchema, UpdateTripSchema } from "../../schemas/trips.schema";
@@ -189,8 +189,8 @@ export default async function tripsRoutes(
     "/last-km/:vehicleId",
     { preHandler: requirePermission("trips.manage") },
     async (request, reply) => {
-      const vehicleId = parseInt(request.params.vehicleId, 10);
-      if (isNaN(vehicleId)) return error(reply, "Neplatné ID vozidla", 400);
+      const vehicleId = parseId((request.params as any).vehicleId, reply);
+      if (vehicleId === null) return;
 
       const [lastTrip, vehicle] = await Promise.all([
         prisma.trips.findFirst({
@@ -261,8 +261,8 @@ export default async function tripsRoutes(
     "/:id",
     { preHandler: requireAuth },
     async (request, reply) => {
-      const id = parseInt(request.params.id, 10);
-      if (isNaN(id)) return error(reply, "Neplatné ID", 400);
+      const id = parseId((request.params as any).id, reply);
+      if (id === null) return;
       const parsed = parseBody(UpdateTripSchema, request.body);
       if ("error" in parsed) return error(reply, parsed.error, 400);
       const body = parsed.data;
@@ -335,8 +335,8 @@ export default async function tripsRoutes(
     "/:id",
     { preHandler: requireAuth },
     async (request, reply) => {
-      const id = parseInt(request.params.id, 10);
-      if (isNaN(id)) return error(reply, "Neplatné ID", 400);
+      const id = parseId((request.params as any).id, reply);
+      if (id === null) return;
       const authData = request.authData!;
       const existing = await prisma.trips.findUnique({ where: { id } });
       if (!existing) return error(reply, "Jízda nenalezena", 404);
diff --git a/src/schemas/offers.schema.ts b/src/schemas/offers.schema.ts
index bd9f724..ad08637 100644
--- a/src/schemas/offers.schema.ts
+++ b/src/schemas/offers.schema.ts
@@ -6,14 +6,14 @@ const QuotationItemSchema = z.object({
   quantity: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(1),
   unit: z.string().nullish(),
   unit_price: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(0),
   is_included_in_total: z
@@ -23,7 +23,7 @@ const QuotationItemSchema = z.object({
   position: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
 });
 
@@ -34,7 +34,7 @@ const ScopeSectionSchema = z.object({
   position: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
 });
 
@@ -53,7 +53,7 @@ export const CreateQuotationSchema = z.object({
   vat_rate: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(21.0),
   apply_vat: z
@@ -75,7 +75,7 @@ export const UpdateQuotationSchema = z.object({
   customer_id: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
   created_at: z.union([z.string(), z.null()]).optional(),
   valid_until: z.union([z.string(), z.null()]).optional(),
@@ -84,7 +84,7 @@ export const UpdateQuotationSchema = z.object({
   vat_rate: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
   apply_vat: z
     .preprocess((v) => v === true || v === 1 || v === "1", z.boolean())
diff --git a/src/schemas/orders.schema.ts b/src/schemas/orders.schema.ts
index 2da2eff..0f676f2 100644
--- a/src/schemas/orders.schema.ts
+++ b/src/schemas/orders.schema.ts
@@ -6,14 +6,14 @@ const OrderItemSchema = z.object({
   quantity: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(1),
   unit: z.string().nullish(),
   unit_price: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(0),
   is_included_in_total: z
@@ -23,7 +23,7 @@ const OrderItemSchema = z.object({
   position: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
 });
 
@@ -34,7 +34,7 @@ const OrderSectionSchema = z.object({
   position: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
 });
 
@@ -42,7 +42,7 @@ export const CreateOrderFromQuotationSchema = z.object({
   quotationId: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" }),
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" }),
   customerOrderNumber: z.string().optional().default(""),
 });
 
@@ -68,7 +68,7 @@ export const CreateOrderSchema = z.object({
   vat_rate: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(21.0),
   apply_vat: z
@@ -78,7 +78,7 @@ export const CreateOrderSchema = z.object({
   exchange_rate: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional()
     .default(1.0),
   scope_title: z.string().nullish(),
@@ -103,7 +103,7 @@ export const UpdateOrderSchema = z.object({
   vat_rate: z
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
-    .refine((v) => !Number.isNaN(v), { message: "Must be a valid number" })
+    .refine((v) => !Number.isNaN(v), { message: "Musí být platné číslo" })
     .optional(),
   apply_vat: z
     .preprocess((v) => v === true || v === 1 || v === "1", z.boolean())