Refactor code structure for improved readability and maintainability

Co-authored-by: Copilot <copilot@github.com>

flutter/lib/core/api/api_client.dart

@@ -24,7 +24,7 @@ class ApiClient {
         if (token != null) 'Authorization': 'Bearer $token',
       };
 
-  Future<Map<String, dynamic>> getJson(String path, {String? token}) async {
+  Future<dynamic> getJson(String path, {String? token}) async {
     final response = await _client.get(
       Uri.parse('$baseUrl$path'),
       headers: _headers(token: token),

flutter/lib/core/api/api_paths.dart

@@ -28,6 +28,15 @@ class PantryApiPaths {
   static String remove(int id) => '/pantry/$id';
 }
 
+class UserApiPaths {
+  static const me = '/users/me';
+  static const list = '/users';
+  static String setRole(int id) => '/users/$id/role';
+  static String setPremium(int id) => '/users/$id/premium';
+  static String delete(int id) => '/users/$id';
+  static String resetPassword(int id) => '/users/$id/reset-password';
+}
+
 class MealPlanApiPaths {
   static const list = '/meal-plan';