feat: points 11a + 11b — Indicateur AI Actif & Page d'accueil voute

Point 11a — Indicateur AI Actif:
- Badge sync flashe en blanc pendant traitement AI (animation CSS)
- Événements ai-processing-start/end dans ai.js
- Section statut IA dans panneau sync (configurée/non configurée/en cours)
- Endpoint GET /api/ai/status vérifiant les clés API configurées

Point 11b — Page d'accueil de voute:
- Endpoint GET /api/vault/{vault}/files?dir=... (trié par mtime)
- Module vaulthome.js: affichage style résultats de recherche
- Breadcrumb navigable, mise à jour auto sur clic dossier dans tree
- Déclenché auto quand un vault spécifique est sélectionné

frontend/style.css

@@ -3872,6 +3872,184 @@ body.resizing-v {
   }
 }
 
+/* AI processing — white flash on the sync badge */
+.sync-badge--ai-processing {
+  background: #ffffff !important;
+  box-shadow: 0 0 6px 3px rgba(255, 255, 255, 0.6) !important;
+  animation: ai-flash 0.6s ease-in-out infinite;
+}
+
+@keyframes ai-flash {
+  0%, 100% { opacity: 1; box-shadow: 0 0 6px 3px rgba(255,255,255,0.6); }
+  50%      { opacity: 0.3; box-shadow: 0 0 12px 6px rgba(255,255,255,0.9); }
+}
+
+/* ── AI Status section inside sync panel ── */
+
+.sync-panel__ai-section {
+  border-top: 1px solid var(--border);
+  padding: 10px 14px;
+}
+
+.sync-panel__ai-header {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+}
+
+.sync-panel__ai-title {
+  font-size: 0.78rem;
+  font-weight: 600;
+  color: var(--text-primary);
+}
+
+.sync-panel__ai-state {
+  font-size: 0.75rem;
+  display: flex;
+  align-items: center;
+  gap: 5px;
+  padding: 2px 8px;
+  border-radius: 4px;
+}
+
+.sync-panel__ai-state i {
+  flex-shrink: 0;
+}
+
+.sync-panel__ai--active {
+  color: #22c55e;
+  background: rgba(34, 197, 94, 0.1);
+}
+
+.sync-panel__ai--inactive {
+  color: #f59e0b;
+  background: rgba(245, 158, 11, 0.1);
+}
+
+.sync-panel__ai--processing {
+  color: #ffffff;
+  background: rgba(59, 130, 246, 0.2);
+  animation: ai-status-pulse 1s ease-in-out infinite;
+}
+
+.sync-panel__ai--unknown {
+  color: var(--text-muted);
+  background: var(--bg-tertiary);
+}
+
+@keyframes ai-status-pulse {
+  0%, 100% { opacity: 1; }
+  50%      { opacity: 0.6; }
+}
+
+/* ---------------------------------------------------------------------------
+   Vault Home Page
+   --------------------------------------------------------------------------- */
+
+.vault-home {
+  padding: 16px 24px;
+  max-width: 900px;
+  margin: 0 auto;
+}
+
+.vault-home-breadcrumb {
+  display: flex;
+  align-items: center;
+  flex-wrap: wrap;
+  gap: 2px;
+  font-size: 0.85rem;
+  margin-bottom: 16px;
+  padding: 8px 12px;
+  background: var(--bg-secondary);
+  border: 1px solid var(--border);
+  border-radius: 8px;
+}
+
+.vault-home-breadcrumb-item {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  padding: 2px 6px;
+  border-radius: 4px;
+  color: var(--text-secondary);
+  transition: background 0.15s, color 0.15s;
+  user-select: none;
+}
+
+.vault-home-breadcrumb-item:hover {
+  background: color-mix(in srgb, var(--accent) 10%, transparent);
+  color: var(--text-primary);
+}
+
+.vault-home-breadcrumb-root {
+  font-weight: 600;
+  color: var(--accent);
+}
+
+.vault-home-breadcrumb-sep {
+  color: var(--text-muted);
+  user-select: none;
+  font-size: 0.8rem;
+}
+
+.vault-home-header {
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  margin-bottom: 12px;
+  padding-bottom: 8px;
+  border-bottom: 1px solid var(--border);
+}
+
+.vault-home-count {
+  font-size: 0.8rem;
+  font-weight: 600;
+  color: var(--text-primary);
+  background: var(--bg-secondary);
+  padding: 3px 10px;
+  border-radius: 4px;
+}
+
+.vault-home-dir-info {
+  font-size: 0.75rem;
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.vault-home-results {
+  min-height: 200px;
+}
+
+.vault-home-empty {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  padding: 3rem;
+  color: var(--text-muted);
+  gap: 8px;
+}
+
+.vault-home-empty p {
+  font-size: 0.85rem;
+  margin: 0;
+}
+
+.vault-home-error {
+  padding: 2rem;
+  text-align: center;
+  color: var(--danger, #ef4444);
+  font-size: 0.85rem;
+}
+
+.vault-home-item {
+  cursor: pointer;
+}
+
+.vault-home-item:hover {
+  background: var(--bg-secondary);
+}
+
 /* ---------------------------------------------------------------------------
    Sync Panel — event log overlay
    --------------------------------------------------------------------------- */