feat(app): clear all events from the Event Center (red trash icon)

Adds Cmd::ClearEvents + Evt::EventsCleared: the daemon drops the persistent
event log (keeping next_id monotonic), persists, and broadcasts so every
client empties its list. A red trash icon next to 'Mark all read' triggers it;
disabled when the list is empty. Threaded through proto, the daemon handler,
the Tauri bridge, and socketBridge. Includes an EventLog::clear test.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src-tauri/src/lib.rs

@@ -52,6 +52,7 @@ pub fn run() {
             bridge::set_zoom,
             bridge::event_log,
             bridge::mark_read,
+            bridge::clear_events,
             bridge::health,
             bridge::get_config,
             bridge::set_config,