feat: release undergraduate integration 0.7.0

mobile/lib/app/app_version.dart

@@ -1,2 +1,2 @@
-const appVersion = '0.6.2';
-const appBuildNumber = 17;
+const appVersion = '0.7.0';
+const appBuildNumber = 18;

mobile/lib/app/hepan_app.dart

@@ -81,8 +81,7 @@ class _Shell extends StatefulWidget {
 class _ShellState extends State<_Shell> with WidgetsBindingObserver {
   int _tab = 0;
   bool _openingSchool = false;
-  // Earlier imports all belong to UESTC graduate; reuse their existing term
-  // and session without requiring students to choose again on every refresh.
+  // Restore the saved school; legacy graduate imports infer their source.
   SupportedSchool? get _knownSchool =>
       widget.controller.snapshot.selectedSchool ??
       (widget.undergraduate?.canLogout == true
@@ -199,6 +198,7 @@ class _ShellState extends State<_Shell> with WidgetsBindingObserver {
           chooseTerm: chooseTerm || term == null,
         );
       }
+      if (!mounted) return;
       await Navigator.push(
         context,
         MaterialPageRoute<void>(builder: (_) => widget.schoolBuilder!()),