Plugin support for custom screensavers and local network access

I'm looking at building (well... using an AI to help me build) an Immich photo screensaver plugin for Tessera, but there are a few limitations in the current plugin system that make this difficult based on the initial assessment done by codex.

Would it be possible to expand the plugin API to support:

• Custom screensavers: Allow plugins to provide their own screensaver types that can be selected and configured alongside the existing options.
• Local network access: Allow plugins to communicate with services hosted locally, with explicit user approval and restrictions on which hosts they can access.
• Backend functionality: Allow plugins to use the Tessera Screen Manager as a broker for more complex integrations. Currently plugins can't run backend code, and the existing fetch system is fairly limited. Ideally, the manager could handle authentication, API requests, image retrieval, resizing and caching, rather than having the ESP32 do this itself.

For Immich specifically, I'd like to support displaying photos from selected albums, people or tags, with shuffle, adjustable intervals and optional overlays for the clock, date and photo information.

I think these additions could open up quite a few possibilities beyond Immich too, particularly for plugins that need to interact with self-hosted services or provide more advanced functionality without requiring changes to Tessera's core code.