Add favorite toggle to yoga poses

Exercises and workouts both have a favorite toggle; yoga poses had an
otherwise identical browse/filter UX but no way to favorite them - an
inconsistency rather than a deliberate omission. Mirrors the existing
exercise/workout favorite pattern exactly: a pivot table, a
belongsToMany on User, and a toggle button on the pose detail page.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

tests/Feature/FavoriteTest.php

@@ -5,6 +5,7 @@ namespace Tests\Feature;
 use App\Models\Exercise;
 use App\Models\User;
 use App\Models\Workout;
+use App\Models\YogaPose;
 use Illuminate\Foundation\Testing\RefreshDatabase;
 use Tests\TestCase;
 
@@ -44,4 +45,25 @@ class FavoriteTest extends TestCase
         $this->actingAs($user)->post(route('workouts.favorite', $workout));
         $this->assertFalse($user->favoriteWorkouts()->where('workout_id', $workout->id)->exists());
     }
+
+    public function test_guest_cannot_favorite_a_yoga_pose(): void
+    {
+        $pose = YogaPose::factory()->create();
+
+        $response = $this->post(route('yoga.favorite', $pose));
+
+        $response->assertRedirect(route('login'));
+    }
+
+    public function test_user_can_toggle_yoga_pose_favorite(): void
+    {
+        $user = User::factory()->create();
+        $pose = YogaPose::factory()->create();
+
+        $this->actingAs($user)->post(route('yoga.favorite', $pose));
+        $this->assertTrue($user->favoriteYogaPoses()->where('yoga_pose_id', $pose->id)->exists());
+
+        $this->actingAs($user)->post(route('yoga.favorite', $pose));
+        $this->assertFalse($user->favoriteYogaPoses()->where('yoga_pose_id', $pose->id)->exists());
+    }
 }