ci: Speed up DB integration tests via Postgres template DB + persistent Jest workers (#31778)

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

.github/workflows/ci-pull-requests.yml

@@ -120,7 +120,14 @@ jobs:
               packages/cli/test/integration/**
               packages/cli/test/migration/**
               packages/cli/test/shared/db/**
+              packages/cli/test/setup-testcontainers.js
+              packages/cli/test/teardown-testcontainers.js
+              packages/cli/jest.config.integration.js
+              packages/cli/jest.config.integration.testcontainers.js
+              packages/cli/jest.config.migration.js
+              packages/cli/jest.config.migration.testcontainers.js
               packages/@n8n/db/**
+              packages/@n8n/backend-test-utils/**
               packages/cli/**/__tests__/**
               packages/testing/containers/services/postgres.ts
               .github/workflows/test-db-reusable.yml

.github/workflows/test-db-reusable.yml

@@ -26,7 +26,11 @@ jobs:
             migration-cmd: pnpm test:sqlite:migrations
             collectCoverage: 'false'
           - name: Postgres 16
-            runner: blacksmith-8vcpu-ubuntu-2204
+            # 4vcpu is enough since persistent-worker + template-DB make PG16
+            # complete in ~480s, which is now close to the SQLite leg (~360s)
+            # — the matrix wall is bounded by the slower leg, so the larger
+            # 8vcpu runner buys headroom we can't cash in anywhere.
+            runner: blacksmith-4vcpu-ubuntu-2204
             test-cmd: pnpm test:postgres:integration:tc
             migration-cmd: pnpm test:postgres:migrations:tc
             TEST_IMAGE_POSTGRES: 'postgres:16'