Complete training workflow and acceptance hardening

docker-compose.test-db.yml

@@ -0,0 +1,15 @@
+services:
+  postgres:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: lct_test
+      POSTGRES_PASSWORD: lct_test
+      POSTGRES_DB: lct_test
+    # Ephemeral storage only: no bind/named volume, never reuses the dev DB.
+    ports:
+      - "127.0.0.1::5432"
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U lct_test -d lct_test"]
+      interval: 2s
+      timeout: 2s
+      retries: 30