fix: avatar fallback, custom emoji remove, Welcome Team roster

[Chessing234]

Summary

• Keep the cached avatar visible after a live URL blip instead of sticking on the monogram ([Bug] User avatar briefly disappears and falls back to monogram circle #2665)
• Match custom emoji reactions by normalized shortcode when removing (CLI + desktop)
• Don’t add Welcome Team bots to a channel when those names are already members ([Bug] Second Desktop install creates duplicate agent identities, inflating channel membership #2648)

Test plan

• Trigger a transient avatar load failure with a local data URL present → monogram should not stick
• buzz reactions add --emoji party --emoji-url … then buzz reactions remove --emoji party
• Second Desktop install against a community that already has Fizz/Honey/Bumble → channel roster does not double

Made with Cursor

[Chessing234]

Rebased onto latest main to pick up nostr 0.44.6 (RUSTSEC-2026-0216) and the file-size ratchet baseline. Local Desktop file-size check is clean against current main.

CI workflows are waiting on maintainer approval for this fork push — please Approve and run workflows when you can.