feat(F-002): database foundation with migrations and dev compose

- node-pg-migrate + pg: baseline migration (extensions, app_meta) with working down
- src/infrastructure/db fail-fast pool and typed query helper
- docker-compose: postgres:16-alpine + redis:7-alpine with one-command up
- table naming convention <module>_<table> documented in README
- integration tests (6) against real PostgreSQL; strict identifier validation
  for test DDL after security-gate hardening round
- deps justified in spec/tech.md; all gates approved; verify.sh green

project/docker-compose.yml

@@ -0,0 +1,30 @@
+services:
+  postgres:
+    image: postgres:16-alpine
+    container_name: mdv-dev-postgres
+    environment:
+      # Dev-only credentials. Public by design, never reuse them outside local dev.
+      POSTGRES_USER: mdv
+      POSTGRES_PASSWORD: mdv_dev_only
+      POSTGRES_DB: mercadodevida
+    ports:
+      - '5432:5432'
+    volumes:
+      - mdv_pg_data:/var/lib/postgresql/data
+    healthcheck:
+      test: ['CMD-SHELL', 'pg_isready -U mdv -d mercadodevida']
+      interval: 2s
+      timeout: 3s
+      retries: 30
+
+  redis:
+    image: redis:7-alpine
+    container_name: mdv-dev-redis
+    ports:
+      - '6379:6379'
+    volumes:
+      - mdv_redis_data:/data
+
+volumes:
+  mdv_pg_data:
+  mdv_redis_data: