fix: prevent double prekey upload when concurrent uploads race on count=0

uploadPreKeys() waited for a concurrent upload but then proceeded to upload
again. With top-up logic and count=0, both handleEncryptNotification and
uploadPreKeysToServerIfRequired fire simultaneously, both see count=0, first
wins and uploads 800, second waits then uploads another 800 → 1600 prekeys.

Fix: return immediately after awaiting the concurrent upload — it already
replenished the pool.

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

src/Socket/socket.ts

@@ -701,10 +701,12 @@ export const makeSocket = (config: SocketConfig) => {
 			}
 		}
 
-		// Prevent multiple concurrent uploads
+		// Prevent multiple concurrent uploads — if one is already running, wait for it and return:
+		// the concurrent upload already replenished the pool, so there is nothing left to do.
 		if (uploadPreKeysPromise) {
 			logger.debug('Pre-key upload already in progress, waiting for completion')
 			await uploadPreKeysPromise
+			return
 		}
 
 		const uploadLogic = async () => {