ci: add Redis sidecar to tests workflow (D-30)

Phase 26 introduced 11 integration tests (test_agent_task_router.py,
test_agent_tracklists.py) that require live Redis at PHAZE_REDIS_URL.
SAQ Queue.from_url is not compatible with fakeredis at saq>=0.26.3, so
these tests have no fakeredis fallback and were failing in CI.

Adds redis:7-alpine service container and PHAZE_REDIS_URL env, mirroring
the existing postgres service pattern.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: SimplicityGuy

.github/workflows/tests.yml

@@ -30,9 +30,19 @@ jobs:
           --health-interval 5s
           --health-timeout 5s
           --health-retries 5
+      redis:
+        image: redis:7-alpine
+        ports:
+          - 6379:6379
+        options: >-
+          --health-cmd "redis-cli ping"
+          --health-interval 5s
+          --health-timeout 5s
+          --health-retries 5
     env:
       DATABASE_URL: >-
         postgresql+asyncpg://phaze:phaze@localhost:5432/phaze_test
+      PHAZE_REDIS_URL: redis://localhost:6379/0
     steps:
       - name: 🔀 Checkout repository
         uses: actions/checkout@v6