Clear cancelled pairing requests when Android disconnects

[enaboapps]

Problem

Cancelling pairing on Android closes its BLE connection, but Switchify PC keeps the pending verification request visible until the two-minute expiry. This leaves stale approval UI and obscures the actual connection lifecycle.

Expected behavior

• macOS removes only pending requests associated with the unsubscribed CoreBluetooth central.
• Windows removes pending requests when the final subscribed client disconnects.
• The UI returns immediately to the waiting state and records a sanitized cancellation activity.
• Approval, rejection, replacement, simultaneous requests, and natural expiry remain unchanged.

This fix must remain compatible with existing Android versions and requires no protocol change.