fix(test): fix 17 pre-existing unit test failures and add astrolabe CI build

Unit test fixes:
- test_userinfo_routes: patch nextcloud_httpx_client instead of httpx.AsyncClient
- test_instrument_tool: patch trace_operation in metrics module (where imported)
- test_management_app_password_endpoints: patch nextcloud_httpx_client and
  get_settings at correct import locations
- test_management_status_endpoint: patch detect_auth_mode and get_settings at
  correct import locations (api.management, not config/config_validators)
- test_token_exchange: fix TokenBrokerService constructor args (client_id/
  client_secret instead of encryption_key)

CI:
- Add Node.js setup and astrolabe build step (composer + npm ci + npm run build)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/server/auth/test_userinfo_routes.py

@@ -34,7 +34,7 @@ async def test_query_idp_userinfo_success(mocker):
     mock_client.__aexit__.return_value = None
 
     mocker.patch(
-        "nextcloud_mcp_server.auth.userinfo_routes.httpx.AsyncClient",
+        "nextcloud_mcp_server.auth.userinfo_routes.nextcloud_httpx_client",
         return_value=mock_client,
     )
 
@@ -59,7 +59,7 @@ async def test_query_idp_userinfo_failure(mocker):
     mock_client.__aexit__.return_value = None
 
     mocker.patch(
-        "nextcloud_mcp_server.auth.userinfo_routes.httpx.AsyncClient",
+        "nextcloud_mcp_server.auth.userinfo_routes.nextcloud_httpx_client",
         return_value=mock_client,
     )