feat(studio): /studio content table + bulk visibility / bulk delete

Skeleton for the creator studio surface deferred since Phase 6. The
/studio route lands on a filterable table of the signed-in user's
videos — All / Public / Unlisted / Private / Shorts / Processing-or-
Failed — with headline totals (public / unlisted / private counts,
processing + failed, total views) in a stat strip above.

Each row shows thumbnail + title + stripped description preview +
visibility badge + per-video totals. Row-level checkboxes raise a
toolbar when any row is selected; the toolbar supports:
  - Change visibility across the selection (any of the three visibility
    enums).
  - Delete the selection with a confirm prompt.

Server-side the bulk endpoints owner-filter by Auth::id() so a crafted
request body can't flip or delete anyone else's videos. Response is
JSON { updated | deleted : N } so the page can reload / toast cleanly.

Sidebar now carries a persistent "Studio" link under the You section
alongside History / Liked Videos.

Analytics, stepped upload (Details → Visibility), and schedule remain
future work — this ships the content management surface, nothing else.

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

routes/web.php

@@ -177,6 +177,11 @@ Route::middleware(['auth', 'verified'])->group(function () {
     Route::get('/liked', [UserController::class, 'liked'])->name('liked');
     Route::get('/feed/subscriptions', [UserController::class, 'subscriptionsFeed'])->name('subscriptions.feed');
 
+    // Creator studio
+    Route::get('/studio',                      [\App\Http\Controllers\StudioController::class, 'index'])->name('studio');
+    Route::post('/studio/bulk/visibility',     [\App\Http\Controllers\StudioController::class, 'bulkVisibility'])->name('studio.bulkVisibility');
+    Route::post('/studio/bulk/delete',         [\App\Http\Controllers\StudioController::class, 'bulkDelete'])->name('studio.bulkDelete');
+
     // Logout all other devices
     Route::post('/settings/logout-all-devices', [UserController::class, 'logoutAllDevices'])->name('settings.logoutAllDevices');