feat: refactor server with shelf_static, return JSON responses, add API docs

bin/server.dart

@@ -4,6 +4,8 @@ import 'dart:async';
 import 'package:shelf/shelf.dart';
 import 'package:shelf/shelf_io.dart';
 import 'package:shelf_router/shelf_router.dart';
+import 'package:shelf_cors_headers/shelf_cors_headers.dart';
+import 'package:shelf_static/shelf_static.dart';
 
 import 'database/database_provider.dart';
 import 'routes/auth_routes.dart';
@@ -22,12 +24,17 @@ void main(List<String> args) async {
 
   final router = Router()
     ..mount('/', authRoutes.routes.call)
-    ..mount('/', geoRoutes.routes.call)
-    ..get('/', (Request req) => Response.ok('Family Safety Tracker API\n'));
+    ..mount('/', geoRoutes.routes.call);
+
+  final staticHandler = createStaticHandler('web', defaultDocument: 'index.html');
 
   final handler = Pipeline()
+      .addMiddleware(corsHeaders())
       .addMiddleware(logRequests())
-      .addHandler(router.call);
+      .addHandler(Cascade()
+          .add(staticHandler)
+          .add(router.call)
+          .handler);
 
   final ip = InternetAddress.anyIPv4;
   final port = int.parse(Platform.environment['PORT'] ?? '9090');