color: input colorspace auto-detection, HDR export tags, LGG/white balance nodes, more LUT formats, waveform parade

- media color primaries/transfer tags now flow from the FFmpeg probe
  through VideoParams into Footage::get_colorspace_to_use(); precedence
  is user override > media tags > project default
- export nclc tags derive from the output colorspace (PQ/HLG/BT.2020,
  P3, sRGB, Rec.601, Rec.709) instead of hardcoded BT.709
- new OCIO Color Grading (Log) node (lift/gamma/gain) and White Balance
  node (kelvin temperature + tint, HDR-safe)
- LUT whitelist extended to 9 OCIO-supported formats
- waveform scope gains an RGB parade mode (GPU and software paths)
- tests updated for the new colorspace precedence

app/codec/ffmpeg/ffmpegdecoder.cpp

@@ -677,6 +677,8 @@ FootageDescription FFmpegDecoder::probe(const QString &filename,
 				stream.set_color_range(info.color_range == fb_color_range_jpeg ?
 										   VideoParams::k_color_range_full :
 										   VideoParams::k_color_range_limited);
+				stream.set_color_primaries(info.color_primaries);
+				stream.set_color_transfer(info.color_trc);
 				stream.set_premultiplied_alpha(false);
 
 				desc.add_video_stream(stream);