fix(web-ui): display all human-facing timestamps in Asia/Jerusalem (deterministic)

Storage stays UTC (DB TIMESTAMPTZ, API ISO-UTC) — only the display layer is
localized, and now deterministically: every timestamp renders pinned to
Asia/Jerusalem via a single Intl-based formatter, so SSR (UTC container) and
the browser agree on any runtime. No layout/visible-format change — only the tz.

- New single date formatter web-ui/src/lib/format-date.ts (G2): formatDate /
  formatDateShort / formatDateLong / formatDateTime / formatDateTimeFull /
  formatTime / formatIsoDate + Israel helpers getIsraelYear / israelDayKey /
  israelMidnightMs / israelParts + formatRelative (long/short/tight wording).
- Routed all ad-hoc toLocaleDateString/toLocaleTimeString/toLocaleString +
  hand-rolled new Date(...).get*() / toISOString().slice(0,10) timestamp call
  sites (30 files) through it. Number toLocaleString left untouched.
- Spec: added INV-UI9 to docs/spec/X6 (UTC storage, Asia/Jerusalem display).

Display-only; no layout/design/IA change → Claude Design gate N/A.
Invariants: G2 (single date formatter, no parallel ad-hoc formatting), INV-UI9.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web-ui/src/components/cases/documents-panel.tsx

@@ -24,6 +24,7 @@ import { apiRequest } from "@/lib/api/client";
 import { casesKeys } from "@/lib/api/cases";
 import type { CaseDetail, CaseDocument } from "@/lib/api/cases";
 import { DocumentTypeEditor } from "@/components/cases/document-type-editor";
+import { formatDateShort as formatDate } from "@/lib/format-date";
 
 /*
  * Document list for the case detail "מסמכים" tab. Uses the real document
@@ -76,15 +77,6 @@ function StatusIcon({ status }: { status: string }) {
   }
 }
 
-function formatDate(iso: string) {
-  if (!iso) return "—";
-  try {
-    return new Date(iso).toLocaleDateString("he-IL");
-  } catch {
-    return iso;
-  }
-}
-
 function filenameFromPath(path: string): string {
   const parts = path.split("/");
   return parts[parts.length - 1] || path;