refactor(codec): de-Qt oakcodec and wrap it in a pure C ABI; switch common handles to refcounted value structs

- oakcodec: de-Qt all 20 sources (QThread decode loop -> std::thread,
  QObject/signals -> callbacks), pure C ABI in include/codec with
  refcounted neutral handles (OakFrame/OakDecoder/OakEncoder),
  framemanager moved in from render, frame_to_buffer/buffer_to_frame
  moved in from oakcommon oiioutils, codec->task via submit callback
  (M8 will register), all cross-module calls go through the other
  side's C API, -fvisibility=hidden + OAKCODEC_API
- oakcommon: handles become refcounted value structs
  {ctx, addref, release, abi_version} (FFmpeg-style), pass-by-value
  signatures, free() as release wrapper; init_from_native/get_native
  for copyable value objects; OakCommonXxx renamed to OakXxx
- oakcommon: add logging (log_debug/info/warning/critical with level
  filtering and sink injection) + printf-style oakcommon_log C wrapper
- oakrender: add CancelAtom C API family; complete
  oakrender_color_processor_convert_frame; fix get_processor() missing
  definition and OCIO env var lookup
- tests: oakcommon 174, oaknode 96, oakrender 42, oakcodec 18, all
  green in their standalone builds

include/render/color.h

@@ -22,6 +22,7 @@
 #define OAK_EDITOR_RENDER_COLOR_H
 
 #include "error.h"
+#include "renderer.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -93,6 +94,23 @@ int oakrender_color_processor_convert(OakColorProcessor *processor,
 									  double ia, double *out_r, double *out_g,
 									  double *out_b, double *out_a);
 
+/**
+ * @brief Convert a CPU frame's pixels through the processor, in place
+ * (olive::ColorProcessor::convert_frame()).
+ *
+ * The frame's data buffer is rewritten through an OCIO PackedImageDesc
+ * view; nothing is allocated and the frame handle stays owned by the
+ * caller. A processor whose underlying OCIO processor is null
+ * (oakrender_color_processor_create() treats lookup failure as
+ * non-fatal) is a pass-through and returns OAKRENDER_OK, mirroring the
+ * C++ API.
+ *
+ * @return OAKRENDER_OK, OAKRENDER_E_INVALID for NULL/uninitialized
+ *         arguments, or OAKRENDER_E_FAILED on an internal exception.
+ */
+int oakrender_color_processor_convert_frame(OakColorProcessor *processor,
+											OakCodecFrame *frame);
+
 /* ---- ColorManager statics ------------------------------------------------- */
 
 /**