Add feature test coverage for the core domain

Only Breeze's default auth/profile tests existed - nothing covered
Workouts, Sessions, Exercises, Yoga, Favorites, Blog, or the Admin
panel, which is the actual product. Adds factories for the domain
models and 45 new feature tests covering the main flows plus
authorization boundaries (owner-only access on workouts/sessions,
admin-only access on /admin, drafts hidden from the public blog).

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

app/Models/Post.php

@@ -3,12 +3,15 @@
 namespace App\Models;
 
 use Illuminate\Database\Eloquent\Builder;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Support\Facades\Storage;
 
 class Post extends Model
 {
+    use HasFactory;
+
     protected $fillable = [
         'title',
         'slug',