feat(insurance): redesign insurance management page to match Figma

Rebuild the /admin/insurance-pricing contracts UI to the Figma "مدیریت بیمه"
design and inject the coverage/franchise/ceiling fields the design omitted.

Backend:
- Add contract-level `kind` column to TenantInsurance (basic|supplementary),
  defaulting to the catalog type; migration Version20260715093358.
- POST/PATCH /billing/tenant-insurances now accept effective_from,
  effective_to, kind; PATCH also toggles is_active without clobbering the
  user-set effective_to (unlike DELETE/deactivate).
- List returns the latest version of every insurance (active + inactive) via
  TenantInsuranceRepository::findLatestByTenant, for the فعال/غیرفعال toggle.

Frontend:
- New InsuranceModal (ui/Modal + SearchableSelect + PersianDateInput) with the
  seven fields; submit "ثبت بیمه".
- TenantInsuranceContracts rebuilt: header + search box, desktop table
  (ردیف/نام/کد/نوع/وضعیت/عملیات) and mobile cards, status toggle -> PATCH.
- utils: isoToUnix/unixToIso helpers for contract dates.

Tests: TenantInsuranceContractApiTest (create/edit/toggle/list, 5 cases),
InsuranceModal + TenantInsuranceContracts vitest suites, docs/api updated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/admin/lib/utils.ts

@@ -46,6 +46,17 @@ export function toGregorianDate(d: Date): string {
   return `${y}-${m}-${day}`;
 }
 
+// API stores contract dates as Unix seconds; the date input speaks Y-m-d strings.
+export function isoToUnix(iso: string): number | null {
+  const d = toDate(iso);
+  return d && !isNaN(d.getTime()) ? Math.floor(d.getTime() / 1000) : null;
+}
+
+export function unixToIso(ts: number | null | undefined): string {
+  if (ts == null) return '';
+  return toGregorianDate(new Date(ts * 1000));
+}
+
 export function maskMobile(mobile: string): string {
   if (mobile.length < 7) return mobile;
   return mobile.slice(0, 4) + '***' + mobile.slice(-3);