feat: add beta environment banner

Add beta environment warning banner for Cloud beta deployments with i18n support (zh/en/ja)

src/langbot/pkg/api/http/controller/groups/system.py

@@ -200,11 +200,22 @@ class SystemRouterGroup(group.RouterGroup):
             if invitation_delivery_service is None:
                 invitation_delivery_service = InvitationDeliveryService(self.ap)
 
+            # Detect beta flag from telemetry diagnostics manager
+            is_beta = False
+            diagnostics = getattr(self.ap, 'diagnostics', None)
+            if diagnostics is not None:
+                is_beta = getattr(diagnostics, 'beta', False)
+
+            # Detect Cloud deployment mode
+            is_cloud = getattr(getattr(self.ap, 'deployment', None), 'mode', 'oss') == 'cloud'
+
             return self.success(
                 data={
                     'version': constants.semantic_version,
                     'debug': constants.debug_mode,
                     'edition': constants.edition,
+                    'beta': is_beta,
+                    'deployment_mode': 'cloud' if is_cloud else 'oss',
                     'enable_marketplace': self.ap.instance_config.data.get('plugin', {}).get(
                         'enable_marketplace', True
                     ),