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/pages/ReceivedInvoices.tsx

@@ -148,7 +148,6 @@ export default function ReceivedInvoices({
   const { sort, order, handleSort, activeSort } = useTableSort("created_at");
   const [search, setSearch] = useState("");
 
-  // Data
   const [invoices, setInvoices] = useState<ReceivedInvoice[]>([]);
   const [loading, setLoading] = useState(true);
   const [stats, setStats] = useState<ReceivedStats | null>(null);
@@ -159,7 +158,6 @@ export default function ReceivedInvoices({
   const prevMonth = useRef(statsMonth);
   const prevYear = useRef(statsYear);
 
-  // Modals
   const [editOpen, setEditOpen] = useState(false);
   const [editInvoice, setEditInvoice] = useState<EditInvoice | null>(null);
   const [deleteConfirm, setDeleteConfirm] = useState<{
@@ -169,10 +167,8 @@ export default function ReceivedInvoices({
   const [deleting, setDeleting] = useState(false);
   const [saving, setSaving] = useState(false);
 
-  // Supplier autocomplete
   const [supplierNames, setSupplierNames] = useState<string[]>([]);
 
-  // Upload state
   const [uploadFiles, setUploadFiles] = useState<File[]>([]);
   const [uploadMeta, setUploadMeta] = useState<UploadMeta[]>([]);
   const [uploadErrors, setUploadErrors] = useState<UploadErrors>({});
@@ -180,7 +176,6 @@ export default function ReceivedInvoices({
 
   useModalLock(uploadOpen || editOpen);
 
-  // Slide direction detection
   useEffect(() => {
     const prev = prevYear.current * 12 + prevMonth.current;
     const curr = statsYear * 12 + statsMonth;
@@ -194,7 +189,6 @@ export default function ReceivedInvoices({
     prevYear.current = statsYear;
   }, [statsMonth, statsYear]);
 
-  // Fetch list
   const fetchList = useCallback(async () => {
     if (!hasLoadedOnce.current) setLoading(true);
     try {
@@ -228,7 +222,6 @@ export default function ReceivedInvoices({
     fetchList();
   }, [fetchList]);
 
-  // Fetch supplier names for autocomplete
   useEffect(() => {
     apiFetch(`${API_BASE}/received-invoices/suppliers`)
       .then((r) => r.json())
@@ -277,7 +270,6 @@ export default function ReceivedInvoices({
     load();
   }, [statsMonth, statsYear]);
 
-  // Upload handlers
   const handleFileSelect = (e: React.ChangeEvent<HTMLInputElement>) => {
     const selected = Array.from(e.target.files || []);
     if (selected.length === 0) {
@@ -384,7 +376,6 @@ export default function ReceivedInvoices({
     }
   };
 
-  // Edit handlers
   const toDateInput = (d: string | null | undefined): string => {
     if (!d) return "";
     const date = new Date(d);
@@ -455,7 +446,6 @@ export default function ReceivedInvoices({
     }
   };
 
-  // Delete
   const handleDelete = async () => {
     if (!deleteConfirm.invoice) {
       return;
@@ -484,26 +474,20 @@ export default function ReceivedInvoices({
     }
   };
 
-  // View file
   const openFile = async (inv: ReceivedInvoice) => {
-    const newWindow = window.open("", "_blank");
     try {
       const response = await apiFetch(
         `${API_BASE}/received-invoices/${inv.id}/file`,
       );
       if (!response.ok) {
-        newWindow?.close();
         alert.error("Nepodařilo se načíst soubor");
         return;
       }
       const blob = await response.blob();
       const url = URL.createObjectURL(blob);
-      if (newWindow) {
-        newWindow.location.href = url;
-      }
+      window.open(url, "_blank");
       setTimeout(() => URL.revokeObjectURL(url), 60000);
     } catch {
-      newWindow?.close();
       alert.error("Chyba připojení");
     }
   };
@@ -531,7 +515,6 @@ export default function ReceivedInvoices({
 
   const monthLabel = `${MONTH_NAMES[statsMonth - 1]}`;
 
-  // KPI
   const renderKpi = () => {
     if (!hasLoadedOnce.current && statsLoading) {
       return (