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>

pages/admin/api-docs/spec().php

@@ -0,0 +1,30 @@
+<?php
+
+use MintyPHP\Service\Access\PermissionService;
+use MintyPHP\Support\Guard;
+
+define('MINTY_ALLOW_OUTPUT', true);
+
+Guard::requireLogin();
+Guard::requirePermission(PermissionService::API_DOCS_VIEW);
+
+$projectRoot = dirname(__DIR__, 3);
+$specPath = $projectRoot . '/docs/openapi.yaml';
+
+if (!is_file($specPath)) {
+    http_response_code(404);
+    return;
+}
+
+if (!is_readable($specPath)) {
+    http_response_code(500);
+    return;
+}
+
+header('Content-Type: application/yaml; charset=utf-8');
+header('X-Content-Type-Options: nosniff');
+header('Cache-Control: private, max-age=60');
+$bytes = @readfile($specPath);
+if ($bytes === false) {
+    http_response_code(500);
+}