[Remote] Session history refreshes too slowly

## Bug
The BitFun Remote session history is noticeably stale during active use. Newly created sessions and recent activity do not appear promptly.

## Expected behavior
The session history should update promptly after a session is created or changed, without requiring a manual page refresh.

## Actual behavior
The web client refreshes the session list on a fixed interval of roughly 10 seconds through relay requests. Network/relay queue latency can make the visible delay even longer.

## Reproduction
1. Open BitFun Remote.
2. Create or update a session in the desktop client.
3. Watch the remote session history without manually reloading the page.
4. Observe that the change may remain missing for several seconds.

## Environment
- BitFun 0.2.17
- macOS desktop client
- BitFun Remote web UI via relay

## Suggested direction
Use a session-list event/push signal, or trigger targeted invalidation immediately after session create/update/delete operations. If polling remains necessary, avoid a fixed long interval and prevent overlapping list requests.

Start by tracing the web client's fixed-interval session-list polling and its relay requests, then inspect the session create, update, and delete paths. The change is done when newly created or modified sessions appear promptly without manual refresh, requests do not overlap, and the behavior is verified during active use.

Written by the indexing model from the issue text.