학교 전용 공부 타이머(열품타) + 학년별 랭킹 기능 추가

학생 참여 유도를 위해 공부 시작/종료 타이머와 학년별(오늘/이번주/전체)
랭킹 화면을 대시보드에 추가. 로그인 응답에 학년 정보를 포함시켜
세션 저장/복원 전체 경로에 전달되도록 함.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

lib/function/login_controller.dart

@@ -16,18 +16,21 @@ class LoginResult {
   final String? name;
   final bool isDeviceMatched;
   final String? errorMessage;
+  final int? grade; // 🎓 공부 타이머 학년별 랭킹에서 본인 학년을 기본값으로 쓰기 위함.
 
   const LoginResult.masterSuccess({required this.studentId, required this.name})
     : outcome = LoginOutcome.masterSuccess,
       role = null,
       isDeviceMatched = true,
-      errorMessage = null;
+      errorMessage = null,
+      grade = null;
 
   const LoginResult.needsPasswordChange({
     required this.studentId,
     required this.name,
     required this.role,
     required this.isDeviceMatched,
+    this.grade,
   }) : outcome = LoginOutcome.needsPasswordChange,
        errorMessage = null;
 
@@ -36,6 +39,7 @@ class LoginResult {
     required this.studentId,
     required this.name,
     required this.isDeviceMatched,
+    this.grade,
   }) : outcome = LoginOutcome.success,
        errorMessage = null;
 
@@ -44,7 +48,8 @@ class LoginResult {
       role = null,
       studentId = null,
       name = null,
-      isDeviceMatched = false;
+      isDeviceMatched = false,
+      grade = null;
 }
 
 class LoginController extends ChangeNotifier {
@@ -101,6 +106,7 @@ class LoginController extends ChangeNotifier {
         String name = '';
         String studentId = '';
         int isFirstLogin = 0;
+        int? grade;
 
         var userObj = resData['user'];
         if (userObj != null) {
@@ -114,6 +120,7 @@ class LoginController extends ChangeNotifier {
               userObj['studentId']?.toString() ??
               userObj['student_id']?.toString() ??
               id;
+          grade = int.tryParse(userObj['grade']?.toString() ?? '');
 
           var rawFirst = userObj['isFirstLogin'] ?? userObj['is_first_login'];
           isFirstLogin = (rawFirst is bool)
@@ -126,6 +133,7 @@ class LoginController extends ChangeNotifier {
               resData['studentName']?.toString() ??
               '';
           studentId = resData['studentId']?.toString() ?? id;
+          grade = int.tryParse(resData['grade']?.toString() ?? '');
 
           var rawFirst = resData['isFirstLogin'] ?? resData['is_first_login'];
           isFirstLogin = (rawFirst is bool)
@@ -153,6 +161,7 @@ class LoginController extends ChangeNotifier {
             name: name,
             role: role,
             isDeviceMatched: isDeviceMatched,
+            grade: grade,
           );
         }
 
@@ -161,6 +170,7 @@ class LoginController extends ChangeNotifier {
           studentId: studentId,
           name: name,
           isDeviceMatched: isDeviceMatched,
+          grade: grade,
         );
       } else {
         String errorMsg = '로그인에 실패했습니다.';