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/training/learning-panel.tsx

@@ -9,6 +9,7 @@ import {
   useReconciliationLedger, useStyleDistance, usePairDetail, usePromoteLearning,
   type DraftFinalPair,
 } from "@/lib/api/learning";
+import { formatDateShort as fmtDate } from "@/lib/format-date";
 
 /**
  * /training "למידה" tab (T6/T13) — the reconciliation ledger (INV-LRN4): every
@@ -28,11 +29,6 @@ const STATUS_CLASS: Record<string, string> = {
   lessons_folded: "bg-emerald-50 text-emerald-800 border-emerald-300/60",
 };
 
-function fmtDate(iso: string | null) {
-  if (!iso) return "—";
-  try { return new Date(iso).toLocaleDateString("he-IL"); } catch { return iso; }
-}
-
 function StyleDistanceDetail({ caseNumber }: { caseNumber: string }) {
   const { data, isPending, error } = useStyleDistance(caseNumber);
   if (isPending) return <Loader2 className="w-4 h-4 animate-spin text-ink-muted" />;