M0: Skelett + Auth-Grundgerüst (Keycloak-OIDC + API-Token)

- Symfony 7.4 LTS, PHP 8.4, FrankenPHP, SQLite (3-Layer src/UI|Logic|Data)
- Auth: manueller OidcClient (Authorization-Code) im UI-Layer, kein
  Security-Bundle/league; Session-Gate via SessionAuthSubscriber
- API-Guard via statischem X-Api-Token (ApiTokenSubscriber); ExceptionSubscriber
- UserEntity (Auto-Provision) + Init-Migration
- Docker (php:8.4-frankenphp) + compose (essen.ljh31.de, traefik-net external)
- SmokeTests (7) grün: Redirect-Fälle, API-Token, Auth-Render, Logout

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

config/packages/framework.yaml

@@ -0,0 +1,19 @@
+# see https://symfony.com/doc/current/reference/configuration/framework.html
+framework:
+    secret: '%env(APP_SECRET)%'
+
+    # Note that the session will be started ONLY if you read or write from it.
+    session: true
+
+    http_client:
+        default_options:
+            timeout: 15
+
+    #esi: true
+    #fragments: true
+
+when@test:
+    framework:
+        test: true
+        session:
+            storage_factory_id: session.storage.factory.mock_file