refactor: fix all Low findings from FLAWS_REPORT audit

- Auth: TOTP params from config, JWT error logging, audit log failure
  logging, replaced_by_hash validation on token rotation
- Invoices: remove dead VAT code, consistent PDF permissions,
  WebP magic-byte detection, deduped exchange-rate fetches
- Orders/Offers: multipart limit from config, use paginated() helper,
  payment method from DB in PDF
- Projects: verify project exists before creating note
- Attendance: action_type enum validation, consistent local-time
  shift_date construction, holiday attendance in work fund,
  trips.view permission on last-km query
- Users: paginated() helper usage, remove duplicate dashboard keys,
  parallel currency conversion, single hashToken implementation
- Frontend: memoized customInput, reliable print onload, modal prop
  standardization (isOpen), ConfirmModal type icons, id===0 key
  fallback, Login useCallback, CompanySettings ConfirmModal,
  Attendance timeout cleanup, Dashboard memoization, beforeunload
  dirty-state warnings on Invoice/Offer/Order detail
- Schema: invoice_alert_log timestamp, config/env comment on
  Date.prototype.toJSON override
- Utils: exchange-rate inflight dedup

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/admin/components/AdminDatePicker.tsx

@@ -165,17 +165,22 @@ export default function AdminDatePicker({
     return undefined;
   };
 
-  const commonProps = {
-    selected: toDate(value),
-    onChange: handleChange,
-    locale: "cs",
-    customInput: (
+  const customInput = useMemo(
+    () => (
       <CustomInput
         required={required}
         placeholder={placeholder}
         disabled={disabled}
       />
     ),
+    [required, placeholder, disabled],
+  );
+
+  const commonProps = {
+    selected: toDate(value),
+    onChange: handleChange,
+    locale: "cs",
+    customInput,
     minDate: parseMinMax(minDate),
     maxDate: parseMinMax(maxDate),
     popperPlacement: "bottom-start" as const,