fix: address reader-UI feedback (shorts, search, tags, login, UX)

- Shorts: confirm via youtube.com/shorts/<id> probe (SOCS cookie bypasses the
  consent redirect) instead of a 60s heuristic; concurrent probing, shorts_probed
  flag, scheduled refinement (migration 0005)
- Search: match title + channel name only (descriptions caused noisy results)
- Faceted tag filtering: AND across categories (language AND topic narrows),
  OR within a category; any/all toggle applies to topics
- Language detection: majority vote over individual titles (fixes misdetections
  like multipoleguy -> English; drops bogus Polish/Romanian)
- Login: drop forced consent so returning sign-in is quick (select_account)
- Feed cards: clickable channel name (opens channel), persistent saved badge,
  undo toast on hide, Hidden view to restore; tag chips show counts in tooltip

frontend/src/components/VideoCard.tsx

@@ -80,6 +80,11 @@ function Thumb({ video, className }: { video: Video; className?: string }) {
           stream
         </span>
       )}
+      {video.status === "saved" && (
+        <span className="absolute top-1.5 right-1.5 bg-accent text-accent-fg rounded-full p-1">
+          <Bookmark className="w-3.5 h-3.5" />
+        </span>
+      )}
     </a>
   );
 }
@@ -122,7 +127,15 @@ export default function VideoCard({
         <Thumb video={video} className="w-44 aspect-video shrink-0" />
         <div className="min-w-0 flex-1">
           {title}
-          <div className="text-sm text-muted truncate mt-0.5">{video.channel_title}</div>
+          <a
+            href={video.channel_url}
+            target="_blank"
+            rel="noreferrer"
+            onClick={(e) => e.stopPropagation()}
+            className="text-sm text-muted truncate mt-0.5 block w-fit max-w-full hover:text-fg"
+          >
+            {video.channel_title}
+          </a>
           <div className="text-xs text-muted mt-0.5">{meta}</div>
         </div>
         <Actions video={video} onState={onState} />
@@ -144,7 +157,15 @@ export default function VideoCard({
         )}
         <div className="min-w-0 flex-1">
           {title}
-          <div className="text-sm text-muted truncate mt-0.5">{video.channel_title}</div>
+          <a
+            href={video.channel_url}
+            target="_blank"
+            rel="noreferrer"
+            onClick={(e) => e.stopPropagation()}
+            className="text-sm text-muted truncate mt-0.5 block w-fit max-w-full hover:text-fg"
+          >
+            {video.channel_title}
+          </a>
           <div className="text-xs text-muted mt-0.5">{meta}</div>
           <Actions video={video} onState={onState} />
         </div>