Add video thumbnails and playback in Assets

Video assets now show their first frame as a thumbnail in the grid
instead of a generic Film icon, and the detail modal includes a
video player with controls.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/pages/Assets.jsx

@@ -3,6 +3,7 @@ import { Plus, Upload, Search, FolderOpen, ChevronRight, Grid3X3, X } from 'luci
 import { api } from '../utils/api'
 import AssetCard from '../components/AssetCard'
 import Modal from '../components/Modal'
+import CommentsSection from '../components/CommentsSection'
 
 export default function Assets() {
   const [assets, setAssets] = useState([])
@@ -284,6 +285,11 @@ export default function Assets() {
                 <img src={selectedAsset.url} alt={selectedAsset.name} className="w-full max-h-[400px] object-contain" />
               </div>
             )}
+            {selectedAsset.type === 'video' && selectedAsset.url && (
+              <div className="rounded-lg overflow-hidden bg-surface-tertiary">
+                <video src={selectedAsset.url} controls preload="metadata" className="w-full max-h-[400px]" />
+              </div>
+            )}
             <div className="grid grid-cols-2 gap-4 text-sm">
               <div>
                 <p className="text-text-tertiary">Type</p>
@@ -318,6 +324,7 @@ export default function Assets() {
                 </div>
               </div>
             )}
+            <CommentsSection entityType="asset" entityId={selectedAsset.id || selectedAsset._id} />
             <div className="flex items-center gap-3 pt-4 border-t border-border">
               <button
                 onClick={() => handleDeleteAsset(selectedAsset)}