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/public/theme-init.js

@@ -0,0 +1,12 @@
+// Applies the saved theme before first paint (kept out of index.html so the
+// Content-Security-Policy can forbid inline scripts).
+(function () {
+  try {
+    var t = localStorage.getItem('theme');
+    if (!t) t = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+    var root = document.documentElement;
+    if (t === 'dark') root.classList.add('dark');
+    if (t === 'sepia') root.classList.add('sepia');
+    root.style.colorScheme = t === 'dark' ? 'dark' : 'light';
+  } catch (e) {}
+})();