Tuner v1: HLS pipeline with playback/ingest modes

FFmpeg -> MediaMTX -> HLS relay with runtime-configurable modes:
- PLAYBACK_MODE: standard (mpegts), fmp4 (HEVC), llhls
- INGEST_MODE: rtmp, rtsp
- INGEST_AUDIO_MODE: aac, copy
- Hourly playlist auto-refresh from upstream URL
- Fullscreen video UI with collapsible sidebar, upstream-down banner
- Same-origin HLS proxy for HTTPS deployments

Tagged as the last HLS-based version before the mpegts.js (v2) rework.

backend/models/types.go

@@ -22,11 +22,13 @@ type StreamHealth struct {
 
 // StreamStatus represents the current streaming state.
 type StreamStatus struct {
-	Source      string        `json:"source"`                 // "obs" or "iptv"
-	ChannelName string        `json:"channel_name"`           // current IPTV channel name (empty if OBS)
-	Live        bool          `json:"live"`
-	Transitioning bool       `json:"transitioning"`          // true while switching to a new channel
-	Health      *StreamHealth `json:"health,omitempty"`
+	Source          string        `json:"source"`       // "obs" or "iptv"
+	ChannelName     string        `json:"channel_name"` // current IPTV channel name (empty if OBS)
+	Live            bool          `json:"live"`
+	Transitioning   bool          `json:"transitioning"`    // true while switching to a new channel
+	UpstreamDown    bool          `json:"upstream_down"`    // true when no data is detected from the selected upstream
+	PlaylistVersion int64         `json:"playlist_version"` // increments when playlist reloads
+	Health          *StreamHealth `json:"health,omitempty"`
 }
 
 // ProcessInfo represents the status of a managed child process.