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/api/status.go

@@ -3,8 +3,11 @@ package api
 import (
 	"encoding/json"
 	"net/http"
+	"time"
 )
 
+const upstreamDownAfter = 10 * time.Second
+
 // HandleStatus returns the current stream status as JSON.
 // GET /api/status
 func (a *App) HandleStatus(w http.ResponseWriter, r *http.Request) {
@@ -20,12 +23,26 @@ func (a *App) HandleStatus(w http.ResponseWriter, r *http.Request) {
 	// Attach live stream health metrics when FFmpeg is running
 	status.Health = a.FFmpeg.Health()
 
-	// Auto-clear transitioning once FFmpeg is producing health data
+	// Auto-clear transitioning once FFmpeg is producing health data.
+	// If no progress arrives for a while after a channel switch, flag upstream_down
+	// so all watchers see an "Upstream down?" warning via polling.
 	if status.Transitioning && status.Health != nil && status.Health.Speed != "" {
 		a.mu.Lock()
 		a.Status.Transitioning = false
+		a.Status.UpstreamDown = false
 		a.mu.Unlock()
 		status.Transitioning = false
+		status.UpstreamDown = false
+	} else if status.Transitioning {
+		a.mu.RLock()
+		switchStartedAt := a.SwitchStartedAt
+		a.mu.RUnlock()
+		if !switchStartedAt.IsZero() && time.Since(switchStartedAt) >= upstreamDownAfter {
+			a.mu.Lock()
+			a.Status.UpstreamDown = true
+			a.mu.Unlock()
+			status.UpstreamDown = true
+		}
 	}
 
 	w.Header().Set("Content-Type", "application/json")