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/api/ts.go

@@ -0,0 +1,45 @@
+package api
+
+import (
+	"net/http"
+)
+
+// HandleTS streams the shared channel's raw MPEG-TS bytes to a viewer.
+// Every connected browser subscribes to the same upstream via the hub, so the
+// server holds only one connection to the IPTV source regardless of how many
+// clients are watching.
+// GET /ts
+func (a *App) HandleTS(w http.ResponseWriter, r *http.Request) {
+	flusher, ok := w.(http.Flusher)
+	if !ok {
+		http.Error(w, "streaming unsupported", http.StatusInternalServerError)
+		return
+	}
+
+	w.Header().Set("Content-Type", "video/mp2t")
+	w.Header().Set("Cache-Control", "no-cache, no-store")
+	w.Header().Set("Connection", "keep-alive")
+	w.WriteHeader(http.StatusOK)
+	flusher.Flush()
+
+	sub, unsub := a.Hub.Subscribe()
+	defer unsub()
+
+	ctx := r.Context()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case <-sub.Done():
+			return
+		case chunk, ok := <-sub.Chan():
+			if !ok {
+				return
+			}
+			if _, err := w.Write(chunk); err != nil {
+				return
+			}
+			flusher.Flush()
+		}
+	}
+}