feat: read database uri from secret file

[ArtARTs36]

Adds support for reading the PostgreSQL connection URI from a mounted secret file using DATABASE_URI_PATH.

This makes it possible to provide database credentials through Docker/Kubernetes secrets without putting the connection URI directly into the container environment.

Usage

docker run -i --rm \
  -v /path/to/database-uri:/run/secrets/database-uri:ro \
  -e DATABASE_URI_FILE=/run/secrets/database-uri \
  crystaldba/postgres-mcp --access-mode=unrestricted

The mounted file should contain the PostgreSQL connection URI: postgresql://user:password@host:5432/database

Precedence

The existing behavior remains backward compatible:

• Env DATABASE_URI
• Env DATABASE_URI_FILE
• CLI database URL argument

If both DATABASE_URI and DATABASE_URI_FILE are provided, DATABASE_URI takes precedence.