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/curator-portrait-panel.tsx

@@ -32,6 +32,7 @@ import { Skeleton } from "@/components/ui/skeleton";
 import { ScrollArea } from "@/components/ui/scroll-area";
 import { Tabs, TabsContent, TabsList, TabsTrigger } from "@/components/ui/tabs";
 import { Markdown } from "@/components/ui/markdown";
+import { formatDateShort, formatDateTimeFull } from "@/lib/format-date";
 import {
   useCuratorPrompt,
   useCuratorStats,
@@ -256,7 +257,7 @@ function RecentFindings() {
                 )}
                 <span className="grow text-ink-muted text-end">
                   <Clock className="w-3 h-3 inline me-1" />
-                  {new Date(f.created_at).toLocaleDateString("he-IL")}
+                  {formatDateShort(f.created_at)}
                 </span>
               </div>
               <p className="text-sm text-ink leading-relaxed">{f.lesson_text}</p>
@@ -291,7 +292,7 @@ function CuratorPromptCard() {
             <h3 className="text-navy font-semibold">{data.filename}</h3>
             <p className="text-[0.72rem] text-ink-muted">
               {data.bytes.toLocaleString("he-IL")} בייטים ·
-              עודכן: {new Date(data.last_modified * 1000).toLocaleString("he-IL")}
+              עודכן: {formatDateTimeFull(data.last_modified * 1000)}
             </p>
           </div>
           <Button asChild variant="outline" size="sm">