Improve BLE mesh reliability for large transfers (#964)

* Improve BLE mesh reliability for large transfers

Major reliability improvements for fragment-based transfers (photos, files):

**Notification Queue Fixes**
- Fix silent packet loss when notification queue is full - now queues for retry
- Fix retry queue bug where remaining items were lost when one retry failed
- Add periodic drain mechanism as backup (every 5 seconds)

**Write Queue Fixes**
- Fix drainPendingWrites to use atomic take-send-requeue pattern
- Add logging when peripheral is ready for more writes
- Add periodic drain for pending writes as backup

**Fragment Pacing**
- Increase fragment spacing from 4-5ms to 25-30ms to prevent buffer overflow
- Conservative pacing prevents packet loss on congested BLE connections

**Thread Safety**
- Fix race conditions in stopServices() and emergencyDisconnectAll()
- Synchronize access to peripherals/centrals dictionaries during cleanup
- Clear pending message queues in emergencyDisconnectAll()

**Error Recovery**
- Add handlers for all BLE state transitions (poweredOff, unauthorized, etc.)
- Clear Noise session and re-initiate handshake on decryption failure
- Queue ACKs/receipts for delivery after handshake instead of dropping
- Re-queue failed pending messages for retry

**Other Improvements**
- Add route freshness validation in MeshTopologyTracker (60s threshold)
- Add TTL (24h) and size limits (100 per peer) for MessageRouter outbox
- Fix connection timeout to check peripheral.state before canceling
- Add NoiseEncryptionService.clearSession(for:) method

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Fix race condition and increase test timeouts

- Fix race in sendNoisePayload: use sync barrier instead of async
  to ensure payload is queued before initiating handshake
  (addresses Codex review feedback)

- Increase BLEServiceTests sleep from 0.5s to 1.0s for CI reliability

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

bitchat/Services/NoiseEncryptionService.swift

@@ -616,6 +616,17 @@ final class NoiseEncryptionService {
         }
         rateLimiter.resetAll()
     }
+
+    /// Clear session for a specific peer (e.g., on decryption failure to allow re-handshake)
+    func clearSession(for peerID: PeerID) {
+        sessionManager.removeSession(for: peerID)
+        serviceQueue.sync(flags: .barrier) {
+            if let fingerprint = peerFingerprints.removeValue(forKey: peerID) {
+                fingerprintToPeerID.removeValue(forKey: fingerprint)
+            }
+        }
+        SecureLogger.debug("🔓 Cleared Noise session for \(peerID)", category: .session)
+    }
     
     // MARK: - Private Helpers