Ensure readonly with Postgres transaction

[JakobMiksch]

I recently came across the Postgres MCP, which is a plugin for AI tools. I noticed that they use BEGIN TRANSACTION READ ONLY to make sure everything stays read-only. You can see how they do it here.

The official Postgres docs explain more about starting transactions here.

Using this approach could make things even more secure, just in case someone accidentally runs Postpass with a user that has write permissions.