GCP-03: Cloud Build CI/CD — Kill the Dockerfile Dance

Replace manual deploy procedure (cp Dockerfile, gcloud run deploy --source, cp back) with Cloud Build automation triggered by git push. Current pain: 5 services x 2 regions x manual Dockerfile swap = high error surface. MEMORY.md has 8 lines of deploy warnings. Architecture: 1. Cloud Build triggers per service path 2. Each service gets its own cloudbuild.yaml with correct Dockerfile (no swapping) 3. Artifact Registry: c8-platform repo, keep last 10 images, tags: git-sha + latest 4. Post-deploy smoke test (curl /health), rollback on failure 5. Secret references in cloudbuild.yaml (no secrets in build logs) Deliverables: - cloudbuild.yaml per service (askrosetta-api, c8-cloud-lu, corridor-engine) - Artifact Registry setup - Cloud Build trigger configs - Rollback script: gcloud run deploy --image=PREVIOUS_SHA - Remove all cp Dockerfile instructions from MEMORY.md Target: c8_platform/cloudbuild/ + c8-infra/cloudbuild/