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.

Dockerfile.dev

@@ -3,7 +3,7 @@ RUN corepack enable
 WORKDIR /app
 
 # Install dependencies first for better layer caching.
-COPY package.json pnpm-lock.yaml ./
+COPY package.json pnpm-lock.yaml pnpm-workspace.yaml ./
 RUN pnpm install --frozen-lockfile
 
 COPY . .