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.