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/precedents/precedent-upload-sheet.tsx

@@ -23,6 +23,7 @@ import {
 } from "@/lib/api/precedent-library";
 import { ApiError } from "@/lib/api/client";
 import { useProgress } from "@/lib/api/documents";
+import { formatDateShort } from "@/lib/format-date";
 import {
   PRACTICE_AREAS, PRECEDENT_LEVELS, SOURCE_TYPES,
 } from "./practice-area";
@@ -192,7 +193,7 @@ export function PrecedentUploadSheet({ open, onOpenChange }: Props) {
                   {conflict.citation}
                   {conflict.case_name && ` — ${conflict.case_name}`}
                   {conflict.court && ` · ${conflict.court}`}
-                  {conflict.date && ` · ${new Date(conflict.date).toLocaleDateString("he-IL")}`}
+                  {conflict.date && ` · ${formatDateShort(conflict.date)}`}
                 </p>
                 {conflict.halacha_extraction_status && (
                   <p className="text-danger/60 text-[0.72rem]">