Modernize: remove unused deps, replace qirolab/laravel-themer with custom ThemeService, drop doctrine/dbal

- Remove whichbrowser/parser, mockery/mockery, fruitcake/laravel-debugbar,
  itsgoingd/clockwork (all unused)
- Replace qirolab/laravel-themer (dev-master) with custom App\Services\ThemeService
  and App\Providers\ThemeServiceProvider
- Drop doctrine/dbal: rewrite all ->change() calls in 8 migrations to raw
  DB::statement('ALTER TABLE ... MODIFY ...') SQL
- RenameColumn() kept intact (works without dbal in Laravel 13)
- Fix 2026_04_04 migration: inverted column-exists logic corrected
- Clear bootstrap cache to remove stale references to removed packages

config/app.php

@@ -222,6 +222,7 @@ return [
          */
         AppServiceProvider::class,
         App\Providers\AuthServiceProvider::class,
+        App\Providers\ThemeServiceProvider::class,
         // App\Providers\BroadcastServiceProvider::class,
         EventServiceProvider::class,
         AdminFilamentPanelProvider::class,