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/index.html

@@ -1,15 +1,16 @@
 <!doctype html>
-<html lang="en">
+<html lang="fr">
 
 <head>
   <meta charset="UTF-8" />
   <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
-  <link rel="apple-touch-icon" href="/favicon.svg" />
-  <meta name="theme-color" content="#166534" />
-  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+  <meta name="theme-color" content="#F7F4EC" />
+  <meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover" />
   <meta name="description"
     content="FlowReader - Votre édition quotidienne pour une lecture plaisir et sans distractions." />
+  <meta name="color-scheme" content="light dark" />
   <title>FlowReader | La Une</title>
+  <script src="/theme-init.js"></script>
 </head>
 
 <body>
@@ -17,4 +18,4 @@
   <script type="module" src="/src/main.tsx"></script>
 </body>
 
-</html>
+</html>