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/layouts/RootLayout.tsx

@@ -1,15 +1,24 @@
-import { useState } from 'react';
+import { lazy, Suspense, useState } from 'react';
 import { Sidebar } from '../components/Sidebar';
 import { MobileTopBar } from '../components/MobileTopBar';
 import { DashboardPage } from '../pages/DashboardPage';
-import { FocusPage } from '../pages/FocusPage';
+import { useWebsocket } from '../hooks/useWebsocket';
+
+// Focus mode carries the gesture/animation code: load it only when used.
+const FocusPage = lazy(() => import('../pages/FocusPage').then((m) => ({ default: m.FocusPage })));
 
 export function RootLayout() {
     const [selectedFeedId, setSelectedFeedId] = useState<string | null>(null);
     const [isFocusMode, setIsFocusMode] = useState(false);
 
+    // One socket for the whole session (not per page mount).
+    useWebsocket();
+
     return (
-        <div className="flex h-screen bg-carbon overflow-hidden">
+        <div className="flex h-dvh bg-carbon overflow-hidden">
+            <a href="#main-content" className="sr-only focus:not-sr-only focus:fixed focus:top-2 focus:left-2 focus:z-[80] btn-primary">
+                Aller au contenu
+            </a>
             <Sidebar
                 onSelectFeed={setSelectedFeedId}
                 selectedFeedId={selectedFeedId}
@@ -17,17 +26,28 @@ export function RootLayout() {
                 isFocusMode={isFocusMode}
             />
 
-            {isFocusMode ? (
-                <FocusPage onExit={() => setIsFocusMode(false)} />
-            ) : (
-                <div className="flex-1 flex flex-col min-w-0">
+            <div id="main-content" className="flex-1 flex flex-col min-w-0">
+                {!isFocusMode && (
                     <MobileTopBar
                         onSelectFeed={setSelectedFeedId}
                         selectedFeedId={selectedFeedId}
                         onEnterFocus={() => setIsFocusMode(true)}
                     />
-                    <DashboardPage selectedFeedId={selectedFeedId} onEnterFocus={() => setIsFocusMode(true)} />
-                </div>
+                )}
+                {/* Kept mounted in focus mode so the list keeps its scroll position. */}
+                <DashboardPage selectedFeedId={selectedFeedId} onEnterFocus={() => setIsFocusMode(true)} hidden={isFocusMode} />
+            </div>
+
+            {isFocusMode && (
+                <Suspense
+                    fallback={
+                        <div className="fixed inset-0 z-50 bg-carbon flex items-center justify-center" role="status" aria-label="Chargement">
+                            <div className="w-12 h-12 border-2 border-nature/20 border-t-nature rounded-full animate-spin" />
+                        </div>
+                    }
+                >
+                    <FocusPage onExit={() => setIsFocusMode(false)} />
+                </Suspense>
             )}
         </div>
     );