feat(phase-34): resolve blocking tech debt — Redis, domain exceptions, indexes, CI

Foundational changes required before any new feature work can begin.

- 0.1 Redis infrastructure: add redis:7-alpine to docker-compose dev and prod,
  REDIS_URL config, singleton client in app/infrastructure/redis_client.py
- 0.2 Token blacklist on Redis SEC-001: replace in-memory dict with Redis SETEX
  keyed by jti, auto-expiring TTL derived from token exp
- 0.3 Database indexes SR-006: Alembic migration b019 with 5 composite indexes
  for scoring, MTTD/MTTR, remediation, and notification queries
- 0.4 Domain exceptions TD-003: app/domain/exceptions.py with typed errors,
  error_handler middleware mapping them to HTTP, services decoupled from FastAPI
- 0.5 Fix silenced exceptions TD-007: replace 4 bare except-pass blocks in
  test_workflow_service with logger.warning with exc_info
- 0.6 CI pipeline TD-009: GitHub Actions workflow with Postgres and Redis
  service containers, ruff lint, pytest; ruff.toml for baseline config

backend/tests/test_t106_workflow_service.py

@@ -43,10 +43,19 @@ class _FakeSettings:
     SECRET_KEY = "test"
     ALGORITHM = "HS256"
     ACCESS_TOKEN_EXPIRE_MINUTES = 60
+    REDIS_URL = "redis://localhost:6379/0"
     MINIO_ENDPOINT = "localhost:9000"
     MINIO_ACCESS_KEY = "test"
     MINIO_SECRET_KEY = "test"
     MINIO_BUCKET = "test"
+    MINIO_SECURE = False
+    MAX_RETEST_COUNT = 3
+    CORS_ORIGINS = "http://localhost:3000"
+    SCORING_WEIGHT_TESTS = 40
+    SCORING_WEIGHT_DETECTION_RULES = 20
+    SCORING_WEIGHT_D3FEND = 15
+    SCORING_WEIGHT_FRESHNESS = 15
+    SCORING_WEIGHT_PLATFORM_DIVERSITY = 10
 
 
 config_mod.settings = _FakeSettings()
@@ -105,8 +114,8 @@ from app.services.test_workflow_service import (
     reopen_test,
 )
 
-# We also need HTTPException for assertions
-from fastapi import HTTPException
+# We need the domain exceptions for assertions
+from app.domain.exceptions import InvalidTransitionError
 
 # ---------------------------------------------------------------------------
 # Helpers
@@ -175,9 +184,11 @@ def test_draft_to_validated_fails(mock_log):
 
     try:
         transition_state(db, test, TestState.validated, user)
-        assert False, "Should have raised HTTPException"
-    except HTTPException as exc:
-        assert exc.status_code == 400
+        assert False, "Should have raised InvalidTransitionError"
+    except InvalidTransitionError as exc:
+        assert exc.code == "INVALID_TRANSITION"
+        assert exc.current_state == "draft"
+        assert exc.target_state == "validated"
     print("  [PASS] Transition draft -> validated correctly fails")