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>

resources/views/yoga/show.blade.php

@@ -13,6 +13,22 @@
             <a href="{{ url()->previous() ?? route('yoga.index') }}" class="inline-flex items-center text-sm font-medium text-white/90 hover:text-white">&#8592; {{ __('app.yoga.back') }}</a>
             <div class="mt-3 flex items-start justify-between gap-4">
                 <h1 class="text-3xl sm:text-5xl font-extrabold tracking-tight text-white drop-shadow">{{ $pose->english_name }}</h1>
+                @auth
+                    @php $isFav = auth()->user()->hasFavoritedYogaPose($pose); @endphp
+                    <form method="POST" action="{{ route('yoga.favorite', $pose) }}">
+                        @csrf
+                        <button type="submit" class="inline-flex items-center gap-2 rounded-full bg-white/90 px-3 py-1.5 text-sm font-semibold text-gray-900 shadow hover:bg-white">
+                            <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="currentColor" class="h-5 w-5 {{ $isFav ? 'text-rose-600' : 'text-gray-400' }}">
+                                @if($isFav)
+                                    <path d="M11.645 20.91l-.007-.003-.022-.01a15.247 15.247 0 01-.383-.18 25.18 25.18 0 01-4.244-2.686C4.688 15.734 2.25 13.153 2.25 9.75 2.25 7.005 4.46 4.875 7.125 4.875c1.6 0 3.09.744 4.125 1.917a5.625 5.625 0 014.125-1.917c2.665 0 4.875 2.13 4.875 4.875 0 3.403-2.438 5.984-4.739 7.58a25.175 25.175 0 01-4.244 2.685 15.247 15.247 0 01-.383.18l-.022.01-.007.004-.003.001a.75.75 0 01-.592 0l-.003-.001z"/>
+                                @else
+                                    <path fill-rule="evenodd" d="M12 21.35l-1.45-1.32C5.4 15.36 2 12.28 2 8.5 2 6.01 4.01 4 6.5 4c1.74 0 3.41.81 4.5 2.09A6.004 6.004 0 0115.5 4C17.99 4 20 6.01 20 8.5c0 3.78-3.4 6.86-8.55 11.54L12 21.35z" clip-rule="evenodd"/>
+                                @endif
+                            </svg>
+                            <span>{{ $isFav ? 'Favorited' : 'Favorite' }}</span>
+                        </button>
+                    </form>
+                @endauth
             </div>
             <div class="mt-4 flex flex-wrap items-center gap-2">
                 @if($pose->category)