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/Sidebar.tsx

@@ -15,6 +15,7 @@ const SHOWS = [
   { id: "all", label: "All" },
   { id: "watched", label: "Watched" },
   { id: "saved", label: "Saved" },
+  { id: "hidden", label: "Hidden" },
 ];
 
 function TagChip({
@@ -29,6 +30,7 @@ function TagChip({
   return (
     <button
       onClick={onClick}
+      title={`${tag.channel_count} channel${tag.channel_count === 1 ? "" : "s"}`}
       className={`text-xs px-2.5 py-1 rounded-full border transition ${
         active
           ? "bg-accent text-accent-fg border-accent"
@@ -36,9 +38,6 @@ function TagChip({
       }`}
     >
       {tag.name}
-      <span className={active ? "opacity-80 ml-1" : "text-muted ml-1"}>
-        {tag.channel_count}
-      </span>
     </button>
   );
 }