feat: #59 finalisation mode hors-ligne PWA — badge + conflits

- Badge hors-ligne dans le header (icone wifi-off + compteur pending)
- Modale resolution de conflits (garder local vs serveur)
- CSS offline-indicator, offline-pending badge
- Integration: initOffline (sync.js), cacheViewedFile (viewer.js), searchOffline (search.js)
- IndexedDB: files, content, pending stores avec sync queue
- ROADMAP: #59 marque FAIT

frontend/style.css

@@ -2117,6 +2117,34 @@ select {
   color: var(--accent);
   border-color: var(--accent);
 }
+/* Offline indicator */
+.offline-indicator {
+  display: flex;
+  align-items: center;
+  gap: 6px;
+  padding: 2px 8px;
+  border-radius: 4px;
+  font-size: 0.7rem;
+  cursor: default;
+}
+.offline-indicator.offline {
+  background: var(--warn-bg, rgba(251,191,36,0.12));
+  color: var(--warn);
+  border: 1px solid var(--warn);
+}
+.offline-pending {
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  min-width: 16px;
+  height: 16px;
+  padding: 0 4px;
+  border-radius: 8px;
+  background: var(--warn);
+  color: #000;
+  font-size: 0.6rem;
+  font-weight: 700;
+}
 .saved-search-vault {
   font-size: 0.65rem;
   color: var(--text-muted);