v2: mpegts.js + single-upstream fan-out hub (no FFmpeg/HLS)

Replaces the FFmpeg -> MediaMTX -> HLS pipeline with a raw MPEG-TS
fan-out architecture:

- Go stream.Hub holds ONE upstream connection per active channel and
  broadcasts the raw TS bytes to all connected browsers via /ts.
  The IPTV provider only ever sees one IP (the server), no matter how
  many viewers are watching (shared single-channel model).
- Frontend uses mpegts.js to play the raw TS in-browser via MSE,
  fixing HEVC/H.265 4K streams that HLS could not package.
- Dropped FFmpeg, MediaMTX, RTMP/RTSP, HLS proxy, playback/ingest
  modes, the OBS source toggle, and FFmpeg health stats.
- UI look preserved (fullscreen video, collapsible sidebar, status
  bar, upstream-down banner, hourly playlist auto-refresh).

Tradeoff: loses iOS Safari (no MSE/mpegts.js); fixes desktop/Android
playback of both H.264 and H.265.

backend/models/types.go

@@ -9,38 +9,11 @@ type Channel struct {
 	StreamURL string `json:"stream_url"`
 }
 
-// StreamHealth holds real-time FFmpeg progress metrics for diagnosing issues.
-// Speed < 1x indicates the upstream IPTV source can't deliver fast enough.
-// Drop frames > 0 with speed ~1x suggests local processing issues.
-type StreamHealth struct {
-	Speed      string `json:"speed"`       // "1.00x" — upstream delivery rate
-	FPS        string `json:"fps"`         // frames per second being processed
-	Bitrate    string `json:"bitrate"`     // output bitrate
-	DropFrames string `json:"drop_frames"` // frames dropped by FFmpeg
-	DupFrames  string `json:"dup_frames"`  // frames duplicated by FFmpeg
-}
-
 // 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
-	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.
-type ProcessInfo struct {
-	Running bool   `json:"running"`
-	PID     int    `json:"pid"`
-	Uptime  string `json:"uptime"`
-	Error   string `json:"error,omitempty"`
-}
-
-// SystemStatus holds status for all managed processes.
-type SystemStatus struct {
-	MediaMTX ProcessInfo `json:"mediamtx"`
-	FFmpeg   ProcessInfo `json:"ffmpeg"`
+	ChannelName     string `json:"channel_name"`     // current IPTV channel name
+	Live            bool   `json:"live"`             // true when a channel is selected
+	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
 }