feat: NAS storage for invoices/offers, code cleanup, date/time fixes

- NAS storage for created invoices (PDF via puppeteer), received invoices,
  and offers with auto-save on create/edit
- Deterministic file paths derived from DB fields (no file_path column needed)
- Separate NAS mount points: NAS_FINANCIALS_PATH, NAS_OFFERS_PATH
- Invoice language field (cs/en) stored per invoice, replaces lang modal
- Invoices list filtered by month/year matching KPI card selection
- Centralized date helpers (src/utils/date.ts) replacing all .toISOString()
  calls that returned UTC instead of local time
- Attendance project switching uses exact time (not rounded)
- Comment cleanup: removed ~100 unnecessary/Czech comments
- Removed as-any casts in orders and attendance
- Prisma migrations: add invoice language, drop received_invoices BLOB columns

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/admin/orders.ts

@@ -208,7 +208,7 @@ export default async function ordersRoutes(
       if ("error" in manualParsed) return error(reply, manualParsed.error, 400);
       const body = manualParsed.data;
 
-      const result = await createOrder(body as any);
+      const result = await createOrder(body);
 
       await logAudit({
         request,
@@ -236,7 +236,7 @@ export default async function ordersRoutes(
       const parsed = parseBody(UpdateOrderSchema, request.body);
       if ("error" in parsed) return error(reply, parsed.error, 400);
 
-      const result = await updateOrder(id, parsed.data as any);
+      const result = await updateOrder(id, parsed.data);
       if ("error" in result) return error(reply, result.error!, result.status!);
 
       await logAudit({