Add sub stream recording with adaptive quality playback (#24009)

* add sub stream recording with adaptive quality playback

Optionally record a second, lower bitrate stream alongside the main
recording stream via a `record_sub` input role and `record.sub` config block, with its own retention windows.
Recordings rows now carry the stream type plus the media details needed to serve both streams from one manifest: video codec, audio presence, audio codec and rate, and a record-time keyframe index.

Playback resolves coverage across both streams and merges them into a single VOD sequence, falling back to a discontinuity manifest with per-clip init segments when the media signatures differ. The player exposes a quality selector, and an auto governor picks the stream from stall time, bandwidth, codec support, and the save-data hint.

* fix tests and i18n

frigate/events/cleanup.py

@@ -197,9 +197,11 @@ class EventCleanup(threading.Thread):
 
     def expire_clips(self) -> list[str]:
         ## Expire events from unlisted cameras based on the global config
+        # effective days cover the sub window, keeping tracked objects in
+        # Explore while sub recordings and review items still exist
         expire_days = max(
-            self.config.record.alerts.retain.days,
-            self.config.record.detections.retain.days,
+            self.config.record.effective_alert_days,
+            self.config.record.effective_detection_days,
         )
         file_extension = None  # mp4 clips are no longer stored in /clips
         update_params = {"has_clip": False}
@@ -278,15 +280,13 @@ class EventCleanup(threading.Thread):
 
         ## Expire events from cameras based on the camera config
         for name, camera in self.config.cameras.items():
-            expire_days = max(
-                camera.record.alerts.retain.days,
-                camera.record.detections.retain.days,
-            )
+            # effective days cover the sub window, keeping tracked objects
+            # in Explore while sub recordings and review items still exist
             alert_expire_date = (
-                now - datetime.timedelta(days=camera.record.alerts.retain.days)
+                now - datetime.timedelta(days=camera.record.effective_alert_days)
             ).timestamp()
             detection_expire_date = (
-                now - datetime.timedelta(days=camera.record.detections.retain.days)
+                now - datetime.timedelta(days=camera.record.effective_detection_days)
             ).timestamp()
             # grab all events after specific time
             expired_events = (