fix: add try/catch to delayed PreKey deletion to prevent unhandled rejection

The setTimeout async callback in removePreKey could cause unhandled promise
rejection if the keystore was destroyed (connection closed) before the
5-min grace period expired.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Signal/libsignal.ts

@@ -847,7 +847,11 @@ function signalStorage(
 			// Schedule deletion after grace period
 			const timer = setTimeout(async () => {
 				pendingPreKeyDeletions.delete(keyId)
-				await keys.set({ 'pre-key': { [id]: null } })
+				try {
+					await keys.set({ 'pre-key': { [id]: null } })
+				} catch {
+					// Keystore may be destroyed if connection closed — safe to ignore
+				}
 			}, PREKEY_GRACE_PERIOD_MS)
 
 			pendingPreKeyDeletions.set(keyId, timer)