feat: improve updater flow and release channels

- added dedicated GUI updater executable and integrated launch path from main app

- added stable/beta update channel selection with persisted settings and checker support

- expanded CI/release validation to include updater and full test discovery

tests/test_auth_relogin_smoke.py

@@ -19,7 +19,7 @@ class AuthReloginSmokeTests(unittest.TestCase):
         self.assertIn("process = QProcess(self)", self.main_source)
         self.assertIn("process.start(program, args)", self.main_source)
         self.assertIn("def _on_auth_process_finished(self, exit_code, _exit_status):", self.main_source)
-        self.assertIn("if self.auth_process and self.auth_process.state() == QProcess.NotRunning:", self.main_source)
+        self.assertIn("if self.auth_process and self.auth_process.state() == QProcess.ProcessState.NotRunning:", self.main_source)
 
     def test_force_relogin_has_backoff_and_event_log(self):
         self.assertIn("AUTH_RELOGIN_BACKOFF_SECONDS = 5.0", self.main_source)
@@ -53,7 +53,7 @@ class AuthReloginSmokeTests(unittest.TestCase):
         self.assertIn("class UpdateChecker(QObject):", self.update_source)
         self.assertIn("def _start_auto_update(self, download_url, latest_version, checksum_url=\"\", download_name=\"\"):", self.main_source)
         self.assertIn("AutoUpdateService.prepare_update", self.main_source)
-        self.assertIn("AutoUpdateService.build_update_script", self.main_source)
+        self.assertIn("AutoUpdateService.launch_gui_updater", self.main_source)
 
 
 if __name__ == "__main__":