Add strict types and type hints across API

Apply strict_types and extensive type declarations throughout the API and models, improving type safety and error handling. Key changes: add declare(strict_types=1) to many files; convert properties, method parameters and return values to typed signatures (PDO, arrays, ints, strings, bools, nullables); switch exception handling to Throwable in index and Router; improve Router, controllers and model method signatures and nullability handling; refine file/image serving security checks and headers in ImageController; strengthen Database typing and initialization methods; return explicit types from BaseModel CRUD helpers and counting; update Media/Cast/Adult/Game/Console/Settings controllers and models to use typed methods, better validation, and clearer update/create return types. Also add AGENTS.md (agent skills index), update README with Swagger/OpenAPI usage instructions, and add /.windsurf to .gitignore. These changes aim to harden runtime correctness, make intended contracts explicit, and prepare the codebase for easier maintenance and static analysis.

api/config.php

@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 // Konfiguration
 // Docker-Umgebungsvariablen oder Standardwerte
 define('DB_HOST', getenv('DB_HOST') ?: 'mariadb');
@@ -15,7 +18,7 @@ define('API_LOG_FILE', '/var/www/html/logs/api.log');
 define('PHP_ERROR_LOG_FILE', '/var/www/html/logs/php_error.log');
 
 // Hilfsfunktion für cleanname Generierung
-function generateCleanName($name) {
+function generateCleanName(string $name): string {
     // Kleinbuchstaben, nur alphanumerische Zeichen und Bindestriche
     $clean = strtolower($name);
     // Sonderzeichen durch Bindestriche ersetzen