refactor : reorganize codebase to DDD architecture

Backend:
- src/Api/Auth/State/ — MeProvider, UserPasswordHasherProcessor
- src/Api/Shared/Resource/ — AppVersion
- src/Api/Shared/State/ — AppVersionProvider
- src/Domain/, src/Application/, src/Infrastructure/ — skeleton ready
- User entity stays in src/Entity/ (framework, outside DDD)

Frontend:
- frontend/domains/ — skeleton ready for bounded contexts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Api/Shared/Resource/AppVersion.php

@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Api\Shared\Resource;
+
+use ApiPlatform\Metadata\ApiResource;
+use ApiPlatform\Metadata\Get;
+use App\Api\Shared\State\AppVersionProvider;
+
+#[ApiResource(
+    operations: [
+        new Get(
+            uriTemplate: '/version',
+            provider: AppVersionProvider::class,
+        ),
+    ],
+)]
+class AppVersion
+{
+    public function __construct(
+        public readonly string $version,
+    ) {}
+}