feat: add Swagger UI docs at /api_info endpoint

bin/routes/auth_routes.dart

@@ -7,6 +7,7 @@ import '../database/database_provider.dart';
 import '../middleware/auth_middleware.dart';
 import '../middleware/request_logger.dart';
 import 'dart:convert';
+import 'dart:io';
 
 class AuthRoutes {
   final DatabaseProvider database;
@@ -18,6 +19,7 @@ class AuthRoutes {
     router.post('/login', _login);
     router.post('/reg', _register);
     router.get('/watch', AuthMiddleware(_watch).call);
+    router.get('/api_info', _apiInfo);
     return router;
   }
 
@@ -112,4 +114,12 @@ class AuthRoutes {
     logRequest(method: 'GET', url: '/watch', status: 200, duration: stopwatch.elapsed, responseHeaders: response.headers);
     return response;
   }
+
+  Future<Response> _apiInfo(Request request) async {
+    final swaggerDir = Directory('web/swagger');
+    final swaggerFile = File('${swaggerDir.path}/index.html');
+    final html = await swaggerFile.readAsString();
+    final response = Response(200, body: html, headers: {'Content-Type': 'text/html'});
+    return response;
+  }
 }