Fix seeder: users table has no branch_id column

The seeder was trying to set branch_id on the user, but that column
doesn't exist on the users table (it's on participants/payments).
Removed the branch assignment and unused Branch import.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

database/seeders/DatabaseSeeder.php

@@ -2,7 +2,6 @@
 
 namespace Database\Seeders;
 
-use App\Domain\Identity\Models\Branch;
 use App\Domain\Identity\Models\Role;
 use App\Domain\Shared\Models\Academy;
 use App\Models\User;
@@ -61,12 +60,9 @@ public function run(): void
             ->where('slug', 'academy_owner')
             ->first();
 
-        $branch = Branch::where('academy_id', $academy->id)->first();
-
         $admin->update([
             'role_id' => $ownerRole?->id ?? $admin->role_id,
             'is_super_admin' => true,
-            'branch_id' => $branch?->id ?? $admin->branch_id,
         ]);
 
         if ($ownerRole && !$admin->roles()->where('role_id', $ownerRole->id)->exists()) {