Make it possible to connect to multiple postgres servers

[rsslldnphy]

Is your feature request related to a problem? Please describe.
Because the postgres mcp server takes a connection string as a command line argument, it has to be configured in claude_desktop_config.json. This means that you can only use one database server with Claude Desktop unless you swap out the config file and restart Claude every time you want to change to a different database.

Describe the solution you'd like
It would be great if it was possible to specify multiple databases that you could choose between at prompt time.

Describe alternatives you've considered
A way to specify a different claude_desktop_config.json at the project level, so the mcp servers available differed by project.

Additional context
N/A