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.

.dockerignore

@@ -0,0 +1,17 @@
+.git
+node_modules
+.nuxt
+.output
+.data
+*.log
+.env
+.env.*
+!.env.example
+docker-compose*.yml
+Dockerfile*
+tests
+docs
+tasks
+.DS_Store
+.fleet
+.idea