feat: implement dynamic instance avatar for PeerTube

[geco]

feat: implement dynamic instance avatar for PeerTube

Summary

This PR introduces the ability to dynamically fetch and use the avatar of the specific PeerTube instance being imported, instead of relying on a static default icon. It also exposes a helper method to allow Grayjay clients (Desktop and Mobile) to retrieve this dynamic icon.

Changes

• Dynamic Avatar Fetching: Modified source.enable to fetch the instance configuration from /api/v1/config.
• Version Compatibility: Added logic to handle different PeerTube API versions:
  • For PeerTube < v6, it uses the instance.avatar.path property.
  • For PeerTube >= v6, it selects the last available avatar from the instance.avatars array.
• Fallback Mechanism: If no instance avatar is found or the request fails, the plugin gracefully falls back to the default PeerTube logo.
• Client API Extension: Implemented a getIcon method (exposed via the plugin script) that returns the resolved dynamic avatar URL, enabling Grayjay clients to display instance-specific icons in the UI.

Technical Details

• The fetched avatar path is appended to the instance's base URL and stored in the state object for persistence.
• The implementation ensures that there is no breaking change for instances that do not have a custom avatar configured.