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.theme-dark-green.css

@@ -1,5 +1,6 @@
 @charset "UTF-8";
 
+@layer tokens {
 [data-theme="dark-green"] {
   --app-background-color: #0f1713;
   --app-sidebar-background-color: #0d1511;
@@ -40,3 +41,4 @@
   --app-tile-bg: rgb(20 28 24);
   --app-blockquote-background-color: rgb(20 28 24);
 }
+}