Guard lookups when adding/deleting cameras at runtime (#23994)

* Guard object processor queue handlers against unknown cameras

* Skip embeddings post processing for removed cameras

* End review segments for removed cameras

* Drop queued autotracker moves for removed cameras

* Release tracked event thumbnails when skipping a removed camera

* Add locked accessors for camera states

* Read camera states through the processor accessors

* Guard output and recording paths against cameras not yet known

* Resolve camera state once in ONVIF, notification, and transcription paths

frigate/record/maintainer.py

@@ -745,7 +745,9 @@ class RecordingMaintainer(threading.Thread):
                         regions,
                     ) = data
 
-                    if self.config.cameras[camera].record.enabled:
+                    camera_config = self.config.cameras.get(camera)
+
+                    if camera_config is not None and camera_config.record.enabled:
                         self.object_recordings_info[camera].append(
                             (
                                 frame_time,
@@ -762,7 +764,9 @@ class RecordingMaintainer(threading.Thread):
                         audio_detections,
                     ) = data
 
-                    if self.config.cameras[camera].record.enabled:
+                    camera_config = self.config.cameras.get(camera)
+
+                    if camera_config is not None and camera_config.record.enabled:
                         self.audio_recordings_info[camera].append(
                             (
                                 frame_time,