학번 검색창 폭을 계정 추가 타일과 같게 조정

가로로 길게 늘어지던 검색창을 위쪽 "신규 학생 계정 추가" 타일과
같은 폭(formSquareSize)으로 맞추고, 좁은 화면에서 필터 칩들이
잘리지 않게 Row 대신 Wrap으로 변경.

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

lib/ui/teacher_student_management_page.dart

@@ -767,9 +767,13 @@ class _TeacherStudentManagementPageState
                             ),
                           ),
                           const SizedBox(height: 12),
-                          Row(
+                          Wrap(
+                            crossAxisAlignment: WrapCrossAlignment.center,
+                            spacing: 6,
+                            runSpacing: 8,
                             children: [
-                              Expanded(
+                              SizedBox(
+                                width: isWide ? formSquareSize : 160,
                                 child: TextField(
                                   onChanged: _controller.setSearchQuery,
                                   keyboardType: TextInputType.number,
@@ -792,13 +796,9 @@ class _TeacherStudentManagementPageState
                                   ),
                                 ),
                               ),
-                              const SizedBox(width: 12),
                               _gradeFilterChip(null, '전체'),
-                              const SizedBox(width: 6),
                               _gradeFilterChip(1, '1학년'),
-                              const SizedBox(width: 6),
                               _gradeFilterChip(2, '2학년'),
-                              const SizedBox(width: 6),
                               _gradeFilterChip(3, '3학년'),
                             ],
                           ),