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/schemas/company-settings.schema.ts

@@ -16,7 +16,9 @@ export const UpdateCompanySettingsSchema = z.object({
     .union([z.number(), z.string()])
     .transform((v) => Number(v))
     .optional(),
-  require_2fa: z.preprocess(v => v === true || v === 1 || v === "1", z.boolean()).optional(),
+  require_2fa: z
+    .preprocess((v) => v === true || v === 1 || v === "1", z.boolean())
+    .optional(),
   custom_fields: z.array(z.any()).optional(),
   supplier_field_order: z.array(z.any()).optional(),
 });