feat: add undergraduate import and exam selection screens

mobile/lib/features/profile/import_preview.dart

@@ -10,9 +10,11 @@ class ImportPreview extends StatefulWidget {
     super.key,
     required this.draft,
     required this.controller,
+    this.canApply,
   });
   final ImportDraft draft;
   final AppController controller;
+  final bool Function()? canApply;
   @override
   State<ImportPreview> createState() => _ImportPreviewState();
 }
@@ -41,6 +43,16 @@ class _ImportPreviewState extends State<ImportPreview> {
               style: const TextStyle(color: river),
             ),
             if (draft.semesterLabel != null) Text('学期：${draft.semesterLabel}'),
+            if (widget.controller.snapshot.courses.isNotEmpty &&
+                widget.controller.snapshot.schoolTerm != draft.schoolTerm &&
+                draft.schoolTerm != null)
+              const Padding(
+                padding: EdgeInsets.only(top: 8),
+                child: Text(
+                  '将替换当前课表；导入新学校或新学期后，请重新设置学期开始日。',
+                  style: TextStyle(fontSize: 12, height: 1.6),
+                ),
+              ),
             if (draft.schoolTerm != null)
               const Padding(
                 padding: EdgeInsets.only(top: 8),
@@ -106,6 +118,7 @@ class _ImportPreviewState extends State<ImportPreview> {
                         await widget.controller.applyImport(
                           draft,
                           confirmedEmpty: _clearConfirmed,
+                          canApply: widget.canApply,
                         );
                         if (!context.mounted) return;
                         if (widget.controller.lastError == null) {