Postgres Docker image pins are stale and inconsistent

## Summary The Postgres Docker image pins are currently stale and inconsistent across the public self-host compose file, the development compose file, and the testcontainer setup. Current `master` uses: - `docker-compose.yaml`: `postgres:16.0-alpine` - `dev/docker-compose.dev.yaml`: `postgres:15.5-alpine` - `tests/setup.ts`: `postgres:15.5-alpine` ## Expected behavior Nango's public self-host, local development, and integration-test Postgres containers should use the same supported Postgres major and current patch image, unless there is a specific compatibility reason to keep dev/test on an older major. ## Suggested fix Update the Postgres image pins to `postgres:16.14-alpine`. For the public self-host compose file, this stays within the existing Postgres 16 major line and picks up the current Postgres 16 patch release. For dev and testcontainer usage, this also aligns ephemeral local/test databases with the public self-host baseline. ## Notes Existing self-host users already on the public compose file's Postgres 16 image should be able to move from `16.0-alpine` to `16.14-alpine` as a normal Postgres minor release update. Users with persistent local dev volumes from Postgres 15 would still need the normal major-version handling, or to recreate ephemeral dev data.