Implementa pausa diretta con copertina slate e ripresa.

Metti in pausa ferma RTMP lato app mantenendo la camera aperta, MediaMTX
manda offline.mp4 agli spettatori e Chiudi termina definitivamente.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/controllers/api/v1/stream_sessions_controller.rb

@@ -29,6 +29,11 @@ module Api
         render json: session_json(@session)
       end
 
+      def resume
+        Sessions::Resume.new(@session).call
+        render json: session_json(@session)
+      end
+
       def events
         events = @session.stream_events.recent.limit(100)
         render json: events.map { |e| event_json(e) }

backend/app/controllers/public/regia_controller.rb

@@ -63,6 +63,7 @@ module Public
       closed = @session.terminal?
       {
         status: @session.status,
+        paused: @session.paused?,
         stream_closed: closed,
         live: !closed && (@session.live? || mediamtx_online?(@session)),
         on_air: !closed && mediamtx_online?(@session),