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/unit/test_instrument_tool.py

@@ -32,7 +32,7 @@ def mock_metrics():
 def mock_tracer():
     """Mock OpenTelemetry tracer."""
     with patch(
-        "nextcloud_mcp_server.observability.tracing.trace_operation"
+        "nextcloud_mcp_server.observability.metrics.trace_operation"
     ) as mock_trace:
         # Configure mock to act as a context manager that allows exceptions to propagate
         mock_trace.return_value.__enter__ = MagicMock(return_value=None)