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/admin/hooks/useAttendanceAdmin.ts

@@ -479,7 +479,8 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
 
   // ---- Create modal ----
   const [showCreateModal, setShowCreateModal] = useState(false);
-  const today = new Date().toISOString().split("T")[0];
+  const now = new Date();
+  const today = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, "0")}-${String(now.getDate()).padStart(2, "0")}`;
   const [createForm, setCreateForm] = useState<ShiftFormData>({
     user_id: "",
     shift_date: today,
@@ -589,11 +590,9 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
       try {
         const [yearStr, monthStr] = month.split("-");
 
-        // Build records URL
         let recordsUrl = `${API_BASE}/attendance?year=${yearStr}&month=${monthStr}&limit=1000`;
         if (filterUserId) recordsUrl += `&user_id=${filterUserId}`;
 
-        // Fetch records and balances in parallel
         const [recordsResponse, balancesResponse] = await Promise.all([
           apiFetch(recordsUrl),
           apiFetch(`${API_BASE}/attendance?action=balances&year=${yearStr}`),
@@ -614,7 +613,6 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
         const leaveBalances: Record<string, LeaveBalance> =
           balancesObj?.balances ?? balancesObj ?? {};
 
-        // Compute user_totals client-side
         const userTotals = computeUserTotals(records, usersRef.current, month);
 
         setData((prev) => ({
@@ -670,7 +668,8 @@ export default function useAttendanceAdmin({ alert }: AlertContext) {
   // Create modal
   // =========================================================================
   const openCreateModal = () => {
-    const todayDate = new Date().toISOString().split("T")[0];
+    const d = new Date();
+    const todayDate = `${d.getFullYear()}-${String(d.getMonth() + 1).padStart(2, "0")}-${String(d.getDate()).padStart(2, "0")}`;
     setCreateForm({
       user_id: "",
       shift_date: todayDate,