feat(homekit): add ONVIF motion detection support

- implement ONVIF motion watcher to handle motion events
- add configuration options for motion hold time and ONVIF URL
- remap motion mode from "onvif" to "api" for compatibility
- log ONVIF motion watcher activity for better debugging

feat(onvif): implement event subscription for motion detection
- create PullPoint subscription to receive motion events
- implement methods for pulling messages and renewing subscriptions
- handle event requests and responses specific to motion detection

test(onvif): add unit tests for motion event parsing and subscription
- create tests for parsing various motion event XML responses
- verify correct handling of multiple notifications and edge cases
- test resolving event addresses for ONVIF clients

fix(hksv): improve motion detection logging
- log warnings when accessory or character not found during motion detection
- log number of listeners notified during motion state changes

feat(hap): add listener count method
- introduce method to retrieve the number of listeners for a character

feat(onvif): enhance ONVIF client with event URL handling
- extract event URL from ONVIF device response for subscription management

pkg/hap/character.go

@@ -48,6 +48,10 @@ func (c *Character) RemoveListener(w io.Writer) {
 	}
 }
 
+func (c *Character) ListenerCount() int {
+	return len(c.listeners)
+}
+
 func (c *Character) NotifyListeners(ignore io.Writer) error {
 	if c.listeners == nil {
 		return nil