Add multi-resolution playback support

backend/internal/api/room.go

@@ -48,3 +48,18 @@ func GetActiveRooms(c *gin.Context) {
 
 	c.JSON(http.StatusOK, gin.H{"active_rooms": result})
 }
+
+func GetRoomPlaybackOptions(c *gin.Context) {
+	roomID := c.Param("room_id")
+	qualities := []string{"source"}
+	if adminRTMP != nil {
+		if available := adminRTMP.AvailablePlaybackQualities(roomID); len(available) > 0 {
+			qualities = available
+		}
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"room_id":   roomID,
+		"qualities": qualities,
+	})
+}