feat: select school before connecting timetable

mobile/lib/app/app_version.dart

@@ -1,2 +1,2 @@
-const appVersion = '0.6.1';
-const appBuildNumber = 16;
+const appVersion = '0.6.2';
+const appBuildNumber = 17;

mobile/lib/app/hepan_app.dart

@@ -14,6 +14,7 @@ import '../features/exams/exams_page.dart';
 import '../features/timetable/timetable_page.dart';
 import '../features/profile/profile_page.dart';
 import '../features/school/school_session.dart';
+import '../features/school/school_selection_page.dart';
 
 class HepanApp extends StatelessWidget {
   const HepanApp({
@@ -66,6 +67,16 @@ class _Shell extends StatefulWidget {
 
 class _ShellState extends State<_Shell> with WidgetsBindingObserver {
   int _tab = 0;
+  bool _openingSchool = false;
+  SupportedSchool? _selectedSchool;
+  // Earlier imports all belong to UESTC graduate; reuse their existing term
+  // and session without requiring students to choose again on every refresh.
+  SupportedSchool? get _knownSchool =>
+      _selectedSchool ??
+      (widget.controller.snapshot.schoolTerm != null ||
+              widget.school?.canLogout == true
+          ? SupportedSchool.uestcGraduate
+          : null);
   void _selectTab(int index) {
     if (index == _tab) return;
     setState(() => _tab = index);
@@ -121,7 +132,41 @@ class _ShellState extends State<_Shell> with WidgetsBindingObserver {
     }
   }
 
-  void _school({bool exams = false, bool chooseTerm = false}) {
+  Future<void> _school({
+    bool exams = false,
+    bool chooseTerm = false,
+    bool selectSchool = false,
+  }) async {
+    if (_openingSchool) return;
+    _openingSchool = true;
+    try {
+      var selected = _knownSchool;
+      if (selectSchool || selected == null) {
+        selected = await Navigator.push<SupportedSchool>(
+          context,
+          MaterialPageRoute<SupportedSchool>(
+            builder: (_) => SchoolSelectionPage(selected: _knownSchool),
+          ),
+        );
+        if (!mounted || selected == null) return;
+        setState(() => _selectedSchool = selected);
+      }
+      if (!mounted) return;
+      // The only current connector is the existing UESTC graduate workflow.
+      // A new catalog option must provide its own connector here.
+      switch (selected) {
+        case SupportedSchool.uestcGraduate:
+          await _openSchool(exams: exams, chooseTerm: chooseTerm);
+      }
+    } finally {
+      _openingSchool = false;
+    }
+  }
+
+  Future<void> _openSchool({
+    bool exams = false,
+    bool chooseTerm = false,
+  }) async {
     if (widget.schoolBuilder != null) {
       final term = widget.controller.snapshot.schoolTerm;
       if (exams) {
@@ -135,12 +180,12 @@ class _ShellState extends State<_Shell> with WidgetsBindingObserver {
           chooseTerm: chooseTerm || term == null,
         );
       }
-      Navigator.push(
+      await Navigator.push(
         context,
         MaterialPageRoute<void>(builder: (_) => widget.schoolBuilder!()),
       );
     } else {
-      showDialog<void>(
+      await showDialog<void>(
         context: context,
         builder: (context) => AlertDialog(
           title: const Text('学校认证'),
@@ -275,7 +320,8 @@ class _ShellState extends State<_Shell> with WidgetsBindingObserver {
                           ProfilePage(
                             controller: widget.controller,
                             feedbackSender: widget.feedbackSender,
-                            onLogin: _school,
+                            onLogin: () => _school(selectSchool: true),
+                            schoolName: _knownSchool?.label,
                             onUpdateTerm: () => _school(chooseTerm: true),
                             authStatus: widget.school?.statusLabel ?? '未登录',
                             logoutLabel: widget.school?.logoutFailed == true