fix(test-backend): set REDIS_PASSWORD for Settings validation

Fixed Settings validation error by setting REDIS_PASSWORD to dummy value.

Root cause: Settings model requires REDIS_PASSWORD (required field, line 79
in config.py). Setting it to empty string "" caused Pydantic validation
error: 'Field required'.

Solution: Set REDIS_PASSWORD to 'test-redis-password' (matches test-e2e.yml).
Note that Redis service container has no authentication - password is only
needed to satisfy Settings validation, not actually used for connection.

This aligns with test-e2e.yml pattern which also sets REDIS_PASSWORD to
dummy value despite Redis service container having no auth.

Related to CUR-46

🤖 Generated by Aygentic

Co-Authored-By: Aygentic <[email protected]>

Author: amostt

.github/workflows/test-backend.yml

@@ -91,7 +91,7 @@ jobs:
           SUPABASE_ANON_KEY: test-anon-key
           SUPABASE_SERVICE_KEY: test-service-key
           REDIS_URL: redis://localhost:6379/0
-          REDIS_PASSWORD: ""
+          REDIS_PASSWORD: test-redis-password
           CELERY_BROKER_URL: redis://localhost:6379/0
           CELERY_RESULT_BACKEND: redis://localhost:6379/0
           SECRET_KEY: test-secret-key-for-ci