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>

lib/Service/Settings/ThemeConfigService.php

@@ -0,0 +1,45 @@
+<?php
+
+namespace MintyPHP\Service\Settings;
+
+class ThemeConfigService
+{
+    private const DEFAULT_THEMES = [
+        'light' => 'Light',
+        'dark' => 'Dark',
+    ];
+
+    private static ?array $themes = null;
+
+    public static function all(): array
+    {
+        if (self::$themes !== null) {
+            return self::$themes;
+        }
+
+        $file = dirname(__DIR__, 3) . '/config/themes.php';
+        if (!is_file($file)) {
+            self::$themes = self::DEFAULT_THEMES;
+            return self::$themes;
+        }
+
+        $loaded = include $file;
+        if (!is_array($loaded)) {
+            self::$themes = self::DEFAULT_THEMES;
+            return self::$themes;
+        }
+
+        $clean = [];
+        foreach ($loaded as $key => $label) {
+            $themeKey = strtolower(trim((string) $key));
+            $themeLabel = trim((string) $label);
+            if ($themeKey === '' || $themeLabel === '') {
+                continue;
+            }
+            $clean[$themeKey] = $themeLabel;
+        }
+
+        self::$themes = $clean ?: self::DEFAULT_THEMES;
+        return self::$themes;
+    }
+}