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/attendance.ts

@@ -16,6 +16,7 @@ import {
   UpdateAttendanceSchema,
 } from "../../schemas/attendance.schema";
 import * as attendanceService from "../../services/attendance.service";
+import { localMonthStr } from "../../utils/date";
 
 export default async function attendanceRoutes(
   fastify: FastifyInstance,
@@ -125,7 +126,7 @@ export default async function attendanceRoutes(
 
       const monthStr = query.month
         ? String(query.month)
-        : `${new Date().getFullYear()}-${String(new Date().getMonth() + 1).padStart(2, "0")}`;
+        : localMonthStr(new Date());
       const filterUserId = query.user_id ? Number(query.user_id) : null;
       const data = await attendanceService.getPrintData(monthStr, filterUserId);
       return reply.send({ success: true, data });