feat(ui): badge version visible + FAB AI flottant

frontend/style.css

@@ -522,15 +522,16 @@ a:hover {
   background: color-mix(in srgb, var(--accent) 10%, transparent);
 }
 
-/* Version badge in header */
+/* Version badge in header — always visible */
 .version-badge {
-  display: none;
-  font-size: 10px;
-  color: var(--text-muted);
-  padding: 2px 8px;
+  display: inline-block;
+  font-size: 11px;
+  color: var(--text-secondary);
+  font-weight: 500;
+  padding: 3px 10px;
   border-radius: 10px;
-  background: color-mix(in srgb, var(--text-muted) 8%, transparent);
-  border: 1px solid color-mix(in srgb, var(--text-muted) 15%, transparent);
+  background: color-mix(in srgb, var(--text-secondary) 10%, transparent);
+  border: 1px solid color-mix(in srgb, var(--text-secondary) 20%, transparent);
   font-family: var(--font-mono, monospace);
   white-space: nowrap;
   cursor: default;
@@ -9077,3 +9078,33 @@ body.popup-mode .content-area {
 @media (max-width: 768px) {
   .bookslm-panel { width: 100%; }
 }
+
+/* ── AI Floating Action Button ───────────────────────── */
+.ai-fab {
+  position: fixed;
+  bottom: 24px;
+  right: 24px;
+  width: 52px;
+  height: 52px;
+  border-radius: 50%;
+  background: var(--accent);
+  color: #fff;
+  border: none;
+  cursor: pointer;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  z-index: 99;
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
+  transition: transform 200ms ease, opacity 200ms ease;
+  padding: 0;
+}
+.ai-fab:hover {
+  transform: scale(1.08);
+}
+.ai-fab:active {
+  transform: scale(0.96);
+}
+.ai-fab[hidden] {
+  display: none;
+}