Add configurable rate limiting for dev/stage environments

- Add ORCHARD_LOGIN_RATE_LIMIT env var to Helm deployment template
- Set relaxed rate limit (1000/minute) for dev/stage deployments
- Production keeps strict default (5/minute) for security
- Re-enable auth tests in CI (no longer excluded by marker)
- Update test docstrings to reflect rate limit configuration

backend/tests/integration/test_auth_api.py

@@ -1,15 +1,15 @@
 """Integration tests for authentication API endpoints.
 
 Note: These tests are marked as auth_intensive because they make many login
-requests which can trigger rate limiting on deployed environments. They are
-excluded from CI integration tests but run in local and unit test suites.
+requests. Dev/stage deployments have relaxed rate limits (1000/minute) to
+allow these tests to run. Production uses strict rate limits (5/minute).
 """
 
 import pytest
 from uuid import uuid4
 
 
-# Mark all tests in this module as auth_intensive
+# Mark all tests in this module as auth_intensive (informational, not excluded from CI)
 pytestmark = pytest.mark.auth_intensive