perf(user): cursor + simple pagination on /liked and /history

- /liked: switch Laravel paginate(12) to cursorPaginate(24). Cursor
  pagination matches the Phase 2 feed endpoint pattern: stable across
  inserts (unlike ?page=N which can duplicate or skip rows when a new
  like lands between page fetches) and loads a bounded slice no matter
  how many thousands of likes the user accumulates.
- /history: switch from a get()-all plus in-memory sort to a joined
  simplePaginate(48) at the DB layer. A heavy user who's watched
  thousands of videos would previously fetch every video row into
  memory on each history page load — now the query selects a bounded
  page of (video_views + videos) pairs. Duplicates within a page
  collapse via collect()->unique('id').

Channel videos tab stays non-paginated for now — it needs a dedicated
JSON endpoint before it can share the Phase 2 /videos/feed/more
infinite-scroll wiring. Flagged as follow-up.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

app/Http/Controllers/UserController.php

@@ -325,29 +325,41 @@ class UserController extends Controller
     }
 
     // Watch history
-    public function history()
+    public function history(Request $request)
     {
         $user = Auth::user();
 
-        // Get videos the user has watched, ordered by most recently watched
-        // Include private videos since they are the user's own
-        $videoIds = \DB::table('video_views')
-            ->where('user_id', $user->id)
-            ->orderBy('watched_at', 'desc')
-            ->pluck('video_id')
-            ->unique();
-
-        $videos = Video::whereIn('id', $videoIds)
+        // Latest-first by watched_at. Paginate at the join so a user who
+        // has watched tens of thousands of videos doesn't pull every row
+        // into memory on each page load. Fetch the videos keyed by latest
+        // view so sort order is deterministic even when the same video has
+        // been watched more than once.
+        //
+        // Each history row is one (video_views + videos) pair, with the
+        // uniqueness constraint deferred to presentation: duplicates per
+        // video are expected (one row per view event) and the UI collapses
+        // them with view-count badges.
+        $per = 48;
+        $rows = \DB::table('video_views')
+            ->join('videos', 'videos.id', '=', 'video_views.video_id')
+            ->where('video_views.user_id', $user->id)
             ->where(function ($q) use ($user) {
-                $q->where('visibility', '!=', 'private')
-                    ->orWhere('user_id', $user->id);
+                $q->where('videos.visibility', '!=', 'private')
+                    ->orWhere('videos.user_id', $user->id);
             })
-            ->get()
-            ->sortBy(function ($video) use ($videoIds) {
-                return $videoIds->search($video->id);
-            });
+            ->orderBy('video_views.watched_at', 'desc')
+            ->select('videos.id as id', 'video_views.watched_at')
+            ->simplePaginate($per);
 
-        return view('user.history', compact('videos'));
+        $videoIds = collect($rows->items())->pluck('id')->unique();
+        $videoMap = Video::whereIn('id', $videoIds)->get()->keyBy('id');
+        $videos   = collect($rows->items())
+            ->map(fn ($r) => $videoMap->get($r->id))
+            ->filter()
+            ->unique('id') // collapse re-watches of the same video on this page
+            ->values();
+
+        return view('user.history', ['videos' => $videos, 'paginator' => $rows]);
     }
 
     // Clear watch history
@@ -392,14 +404,18 @@ class UserController extends Controller
     public function liked()
     {
         $user = Auth::user();
-        // Include private videos in liked (user's own private videos)
+        // Include private videos in liked (user's own private videos).
+        // Cursor pagination matches the Phase 2 feed endpoints — stable
+        // across inserts (unlike ?page=N which can duplicate or skip rows
+        // when a new like lands between page fetches) and loads a bounded
+        // slice regardless of how many thousands of likes the user has.
         $videos = $user->likes()
             ->where(function ($q) use ($user) {
                 $q->where('visibility', '!=', 'private')
                     ->orWhere('videos.user_id', $user->id);
             })
-            ->latest()
-            ->paginate(12);
+            ->latest('videos.id')
+            ->cursorPaginate(24);
 
         return view('user.liked', compact('videos'));
     }