feat(web): unified reader with reading settings, faster lists, a11y

- New Reader (desktop + mobile): loads full content on open, prefetches
  the next article, reading progress and time, "Aa" settings (light /
  sepia / dark / auto theme, serif / sans / Atkinson Hyperlegible font,
  size, line height, measure), Space-to-next, keyboard shortcuts, focus
  management, inert background, URL-driven (?a=) so Back closes it.
- Dashboard: cursor pagination, unread/all filter, CSS grid (no masonry),
  no re-sorting under the reader, optimistic cache patches instead of
  refetch storms, "new articles" banner, error/offline states, j/k/o/m/s/v
  shortcuts and help dialog.
- Cards: keyboard-openable, lazy <img>, memoized, touch-only swipe.
- Focus mode: framer drag (drop @use-gesture), Read button, undo restores
  unread state, arrow keys.
- WebSocket: single connection, backoff, cache patching, no console logs.
- Contrast fixes (on-nature tokens), 44px targets, lang="fr", reduced
  motion, self-hosted fonts, theme applied before first paint.
- Code splitting + vendor chunk, prompt-based PWA updates, smaller
  precache, offline cache for opened articles and images, caches cleared
  on logout; upgrade react-router (CVE), drop unused deps and assets.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/UpdateToast.tsx

@@ -0,0 +1,19 @@
+import { useUpdate } from '../stores/updateStore';
+
+/** Offers to load a new app version instead of reloading under the reader. */
+export function UpdateToast() {
+    const apply = useUpdate((s) => s.apply);
+    const dismiss = useUpdate((s) => s.dismiss);
+    if (!apply) return null;
+
+    return (
+        <div
+            role="status"
+            className="fixed bottom-4 left-1/2 -translate-x-1/2 z-[70] flex items-center gap-3 pl-5 pr-2 py-2 rounded-full surface-card animate-rise"
+        >
+            <span className="text-sm text-paper-white">Nouvelle version disponible</span>
+            <button className="btn-primary !min-h-9 !px-4" onClick={apply}>Mettre à jour</button>
+            <button className="btn-ghost !min-h-9 !px-3" onClick={dismiss} aria-label="Plus tard">Plus tard</button>
+        </div>
+    );
+}