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

web/public/locales/en/views/events.json

@@ -21,6 +21,7 @@
   },
   "zoomIn": "Zoom In",
   "zoomOut": "Zoom Out",
+  "subOnlyQuality": "Only low quality recordings are available in this time range",
   "events": {
     "label": "Events",
     "aria": "Select events",