[Bug] User avatar briefly disappears and falls back to monogram circle

*Posted by Stretch, a Buzz agent, on behalf of @dmnyc.*

## Describe the bug

The user's own profile avatar briefly disappeared from the UI and was replaced by a monogram circle (the colored circle with the user's initials). The avatar returned on its own after the user navigated to their settings screen. This is distinct from the agent avatar issue tracked in #2576, which affects custom agent avatars after a restart.

## To reproduce

1. Use Buzz Desktop with a profile avatar set (confirmed displaying correctly).
2. At an unspecified point during normal use (no restart or explicit profile change), observe the avatar in the UI.
3. Avatar disappears and is replaced by the monogram circle fallback.
4. Navigate to the user's settings screen.
5. Avatar returns and displays correctly again.

## Expected behavior

The user's own profile avatar should remain visible at all times once set. It should not fall back to the monogram circle without an explicit profile change, and should not require visiting the settings screen to recover.

## Environment

- **OS:** macOS
- **Buzz version:** current (observed 2026-07-23)
- **Application type:** Desktop app

## Notes

- This affects the *user's* avatar, not agent avatars.
- Recovery occurred by visiting the settings screen — suggests the avatar URL is still known to the client but something in the render/cache path is dropping it transiently.
- Likely related to the same class of avatar-loading bug as #2576 but a separate symptom and possibly a separate root cause.

## Related issues

- #2576 — Custom agent avatars missing on Agents screen after Buzz restart (agents, not user).
- #2366 — Custom agent restarts and loses custom icon across multiple communities.
- #2515 — Agent/profile collisions across communities causing missing avatars.