Converts BLEAnnounceThrottle to a lock-backed class and moves myPeerID/myPeerIDData/myNickname into a lock-backed BLELocalIdentityStateStore snapshot, so announces can never observe a split peer-ID/wire-ID during panic rotation. Serializes sendAnnounce onto the messageQueue barrier and moves the panic-reset pendingNoiseSessionQueues clear onto collectionsQueue (the queue every other mutation site uses).
Rebased onto main after #1431/#1432; integrates with #1431's panic-suspend structure (guard retained in both the outer sendAnnounce and the deferred worker).
