feat: fix favorites display and add star indicator on favorited items

- Add ?metadata=true support to GET /api/files/{id} to return JSON metadata
  instead of binary content (was the root cause of favorites not loading)
- Fix favorites loadFileDetails to use metadata endpoint with auth headers
- Add star icon on favorited files/folders in grid view (top-left corner)
- Add star icon on favorited files/folders in list view (next to name)
- Refresh file view when toggling favorites so star appears/disappears
- Add CSS styles for .favorite-star and .favorite-star-inline

static/css/favorites.css

@@ -92,4 +92,41 @@
 
 .favorite-indicator.active {
     animation: favorite-pulse 0.3s ease;
+}
+
+/* ── Star badge on file/folder cards (normal view) ── */
+
+/* Grid view: star in top-left corner */
+.file-card .favorite-star {
+    position: absolute;
+    top: 8px;
+    left: 8px;
+    font-size: 14px;
+    color: #ffc107;
+    filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.15));
+    z-index: 5;
+    pointer-events: none;
+
+    [dir='rtl'] & {
+        left: unset;
+        right: 8px;
+    }
+}
+
+.file-card .favorite-star.active i {
+    animation: favorite-pulse 0.3s ease;
+}
+
+/* List view: small star next to the name */
+.favorite-star-inline {
+    color: #ffc107;
+    font-size: 11px;
+    margin-left: 6px;
+    vertical-align: middle;
+    filter: drop-shadow(0 0 1px rgba(255, 193, 7, 0.4));
+
+    [dir='rtl'] & {
+        margin-left: 0;
+        margin-right: 6px;
+    }
 }