Add session expiry renewal flow

scripts/ui/main.gd

@@ -12,6 +12,7 @@ var sound_toggle: CheckButton
 var theme_button: Button
 var feedback_button: Button
 var feedback_dialog: Control
+var session_expiry_dialog: Control
 var theme_service
 var current_screen_name := ""
 var screens_margin: MarginContainer
@@ -285,10 +286,15 @@ func _build_ui() -> void:
 	feedback_dialog = preload("res://scripts/ui/app_feedback_dialog.gd").new()
 	feedback_dialog.name = "AppFeedbackDialog"
 	add_child(feedback_dialog)
+	session_expiry_dialog = preload("res://scripts/ui/session_expiry_dialog.gd").new()
+	session_expiry_dialog.name = "SessionExpiryDialog"
+	session_expiry_dialog.logout_requested.connect(_logout)
+	add_child(session_expiry_dialog)
 	_build_account_menu()
 	_build_drawer()
 
 	AuthState.auth_changed.connect(_refresh_header_controls)
+	AuthState.session_expired.connect(_on_session_expired)
 	_refresh_header_controls()
 	_build_app_menu()
 
@@ -682,14 +688,25 @@ func _refresh_theme_button() -> void:
 
 
 func _logout() -> void:
+	_perform_logout("")
+
+
+func _on_session_expired(_reason: String) -> void:
+	_perform_logout("Your session expired. Sign in again.")
+
+
+func _perform_logout(login_message: String) -> void:
 	_close_app_menu()
+	if session_expiry_dialog != null and session_expiry_dialog.has_method("dismiss_for_logout"):
+		session_expiry_dialog.dismiss_for_logout()
 	if BlockSessionService.block_started and BlockSessionService.session_kind != "simulation":
 		BlockSessionService.finish_block()
 	elif BlockSessionService.session_kind == "simulation":
 		BlockSessionService.block_started = false
 	QuestionBankService.clear_questions()
-	AuthState.clear_session()
-	show_screen("login")
+	if AuthState.is_logged_in or not AuthState.access_token.is_empty():
+		AuthState.clear_session()
+	show_screen("login", login_message)
 
 
 func _build_app_menu() -> void: