ci: Coolify autodeploy from main; migrate-on-boot and split dev/prod compose

- Add Nitro plugin to apply Drizzle migrations on server boot (skips when
  DATABASE_URL is unset, e.g. during build).
- Split compose: docker-compose.dev.yml (hot-reload + Postgres) vs
  docker-compose.yml (production/self-host, env-driven, Coolify-deployable).
- Add .dockerignore; parameterise compose env; document the autodeploy
  decision (Coolify watches main, no CI workflow needed) in ADR 0003 and
  plan.md T12.

docker-compose.dev.yml

@@ -0,0 +1,37 @@
+# Local development stack: app with hot-reload (source bind-mounted) + Postgres.
+#   docker compose -f docker-compose.dev.yml up
+services:
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile.dev
+    ports:
+      - "3000:3000"
+    environment:
+      DATABASE_URL: postgres://andon:andon@db:5432/andon
+      HOST: 0.0.0.0
+    depends_on:
+      db:
+        condition: service_healthy
+    volumes:
+      - .:/app
+      - /app/node_modules
+
+  db:
+    image: postgres:16-alpine
+    environment:
+      POSTGRES_USER: andon
+      POSTGRES_PASSWORD: andon
+      POSTGRES_DB: andon
+    ports:
+      - "5432:5432"
+    volumes:
+      - andon_pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U andon"]
+      interval: 5s
+      timeout: 5s
+      retries: 5
+
+volumes:
+  andon_pgdata: