feat(v5): gate V5 to development environments only

Introduce V5Feature and config so V5 routes, jobs, commands, morph maps,
and model queries run only when enabled. Move V5 migrations to
migrations-v5 (loaded only when enabled), remove Flux from production
Docker/install paths, and add isolation tests.

app/Providers/AppServiceProvider.php

@@ -4,6 +4,7 @@ namespace App\Providers;
 
 use App\Models\PersonalAccessToken;
 use App\Models\V5\Application;
+use App\Support\V5\V5Feature;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\Relation;
 use Illuminate\Support\Facades\App;
@@ -29,7 +30,12 @@ class AppServiceProvider extends ServiceProvider
     public function boot(): void
     {
         $this->configureCommands();
-        $this->configureMorphMap();
+
+        if (V5Feature::enabled()) {
+            $this->loadMigrationsFrom(database_path('migrations-v5'));
+            $this->configureMorphMap();
+        }
+
         $this->configureModels();
         $this->configurePasswords();
         $this->configureSanctumModel();