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/bank-accounts.ts

@@ -40,8 +40,7 @@ export default async function bankAccountsRoutes(
           iban: body.iban ? String(body.iban) : null,
           bic: body.bic ? String(body.bic) : null,
           currency: body.currency ? String(body.currency) : "CZK",
-          is_default:
-            !!body.is_default,
+          is_default: !!body.is_default,
           position: body.position ? Number(body.position) : 0,
         },
       });
@@ -107,9 +106,7 @@ export default async function bankAccountsRoutes(
           currency:
             body.currency !== undefined ? String(body.currency) : undefined,
           is_default:
-            body.is_default !== undefined
-              ? !!body.is_default
-              : undefined,
+            body.is_default !== undefined ? !!body.is_default : undefined,
           position:
             body.position !== undefined ? Number(body.position) : undefined,
           modified_at: new Date(),