feat(prekey): add destroy() method for proper resource cleanup

Implements PreKeyManager.destroy() to prevent memory leaks during connection cleanup.

Changes:
- Added PreKeyManager.destroy() method that clears and pauses all PQueues
- Exposed destroy() in SignalKeyStoreWithTransaction type
- Integrated destroy() call in addTransactionCapability() to cleanup both PreKeyManager and keyQueues
- Added keys.destroy() call in socket.ts end() function alongside other cleanup operations

Benefits:
- Prevents memory leaks from orphaned PQueues
- Proper cleanup of PreKeyManager resources during disconnect
- Consistent with existing cleanup pattern (circuit breakers, session manager)
- Zero impact on active connections (only called during cleanup)

Observability:
- Added debug logs for tracking cleanup operations
- Logs include queue type and cleanup status

Cross-file analysis:
- PreKeyManager instantiated in auth-utils.ts:130
- addTransactionCapability() called in socket.ts:499
- cleanup happens in socket.ts:836 (end function)

https://claude.ai/code/session_33db9e93-e4c3-4859-9ff3-96d8864af1c4

src/Types/Auth.ts

@@ -99,6 +99,7 @@ export type SignalKeyStore = {
 export type SignalKeyStoreWithTransaction = SignalKeyStore & {
 	isInTransaction: () => boolean
 	transaction<T>(exec: () => Promise<T>, key: string): Promise<T>
+	destroy?: () => void
 }
 
 export type TransactionCapabilityOptions = {