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

bin/routes/geo_routes.dart

@@ -17,7 +17,7 @@ class GeoRoutes {
   }
 
   Future<Response> _updatePosition(Request request, String login) async {
-    final id = int.parse(request.url.queryParameters['id']!);
+    final id = request.url.queryParameters['id']!;
     final body = await request.readAsString();
     final data = jsonDecode(body);
 
@@ -26,7 +26,7 @@ class GeoRoutes {
 
     await database.updatePosition(id, x, y);
     await database.createLog(login, 'Updated position id=$id');
-    return Response(200);
+    return Response(200, body: jsonEncode({'message': 'Position updated'}), headers: {'Content-Type': 'application/json'});
   }
 
   Future<Response> _createShare(Request request, String login) async {
@@ -43,6 +43,6 @@ class GeoRoutes {
     return Response(201, body: jsonEncode({
       'geo_id': position.id,
       'share_id': shareId
-    }));
+    }), headers: {'Content-Type': 'application/json'});
   }
 }