proposal: Auto update feature in pgAdmin

[dev-hari-prasad]

pgAdmin already checks if a new version is available. This proposal adds a simple way for users to download and install updates directly from pgAdmin.

Problem

Right now, users are told that an update is available, but they still have to download the installer themselves, run it, and reopen pgAdmin.

Proposal

When an update is available, pgAdmin should display an Update available prompt with a Download and install button and a link to the release notes. Once the user chooses to update, pgAdmin should download the installer, verify its integrity before running it, request UAC confirmation, launch the installer, and reopen pgAdmin after the update completes successfully. This keeps the user in control while making the update process much simpler.

[dev-hari-prasad]

I'm willing to update this feature for Windows OS as a starting point. We can later port the same feature to other OSes with minimal changes.