Bring over remainder of legacy desktop frontend elements

We want to do this twofold:
1) We want to have a proper implementation via feature flags into ComfyUI core + comfy frontend repo:
https://github.com/Comfy-Org/ComfyUI_frontend/tree/feat/desktop-terminal-feature-flag
https://github.com/Comfy-Org/ComfyUI/compare/master...feat/supports-terminal-flag

2) While we wait for the proper support, we should create injections into frontend like we did for terminal access.

Start by reviewing the linked ComfyUI_frontend and ComfyUI feature branches, then compare them with the existing terminal-access injections. Done means defining the remaining legacy desktop frontend elements, adding proper feature-flag support across both repositories, and providing interim frontend injections while that support is pending.

Written by the indexing model from the issue text.