Extend packet header with frame processing latency

src/platform/common.h

@@ -186,6 +186,8 @@ namespace platf {
     std::int32_t pixel_pitch {};
     std::int32_t row_pitch {};
 
+    std::optional<std::chrono::steady_clock::time_point> frame_timestamp;
+
     virtual ~img_t() = default;
   };