add composer-unused, comprehensive docs, and project restructure

- Add icanhazstring/composer-unused as dev dependency for dependency hygiene checks
- Add German documentation (docs/) covering architecture, conventions, workflows, and developer checklists
- Add API layer (ApiAuth, ApiBootstrap, ApiResponse), audit, scheduler, custom fields, and SSO services
- Add Microsoft OIDC SSO, API token management, and user lifecycle features
- Add swagger-ui vendor integration and OpenAPI spec
- Add production Docker setup and bin/ scripts
- Update composer dependencies, config, templates, and frontend assets throughout

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

web/css/base/variables.contrast.css

@@ -1,5 +1,6 @@
 @charset "UTF-8";
 
+@layer tokens {
 /* High contrast overrides */
 html[data-contrast="high"][data-theme="light"],
 [data-contrast="high"][data-theme="light"] {
@@ -42,3 +43,4 @@ html[data-contrast="high"][data-theme^="dark"],
   --app-tooltip-background-color: #fff;
   --app-tooltip-color: #0b0f14;
 }
+}