fix: export telemetry routing constants for tests

Export CASE_ROUTING and CASE_TO_TRACE_TASK as module-level constants
to fix import errors in enterprise telemetry tests.

Tests were failing with:
- ImportError: cannot import name 'CASE_ROUTING' from 'core.telemetry.gateway'
- ImportError: cannot import name 'CASE_TO_TRACE_TASK' from 'core.telemetry.gateway'

This fix allows tests to access the routing configuration without breaking
the lazy-loading pattern used internally.

api/core/telemetry/gateway.py

@@ -87,6 +87,10 @@ def _get_case_routing() -> dict:
         }
     return _case_routing
 
+# Public exports for tests and external consumers
+CASE_TO_TRACE_TASK = _get_case_to_trace_task()
+CASE_ROUTING = _get_case_routing()
+
 
 # ---------------------------------------------------------------------------
 # Helpers