R8: finish app/ pure C ABI migration (P3-P9) and make OTIO required

- app/ no longer includes engine C++ headers nor holds engine C++ types:
  engine access goes through the oakengine C ABI plus C++ wrappers
  (oakutil/oaknode.h, oakutil/oakvideo.h) and app-local mirror types
  (tooltypes, trackreferencehandle, timelinecommonapp, keyframetypes,
  subtitleapp, serializedlayoutinfoapp, nodevaluehandle, sliderdisplaytypeapp)
- engine: new C ABI functions for block/track/clip/transition navigation
  and predicates, links, caches, waveform/playback, disk folder,
  sequence_track_list, node_free, footage_is_valid, block_get_track,
  get_brush; loadotio/saveotio ported to the current engine API
- OTIO is now a required dependency: CI and CD build it on every
  platform, FindOpenTimelineIO fixed for OTIO 0.16/0.19 (the old deps
  include requirement silently disabled OTIO everywhere), runtime
  libraries are bundled into packages and copied next to macOS binaries
  (oak_copy_otio_runtime)
- fix ProjectViewModel drag&drop mime read/write size mismatch (segfault)
- unify color label naming (k_olive -> "Oak") in the app-side mirror
- docs: OTIO required, FFmpeg minimum corrected to 6.0 (en/zh)
- gtest suite: 1925 passed, 0 failed

app/widget/timeruler/markerpainting.cpp

@@ -49,7 +49,7 @@ QRect draw(QPainter *p, const QPoint &pt, int max_right, double scale,
 
 	int half_width = marker_width / 2;
 
-	QColor c = QtUtils::to_q_color(ColorCoding::get_color(color));
+	QColor c = QtUtils::to_q_color(AppColorCoding::get_color(color));
 	if (selected) {
 		p->setPen(Qt::white);
 		p->setBrush(c.lighter());
@@ -70,8 +70,8 @@ QRect draw(QPainter *p, const QPoint &pt, int max_right, double scale,
 		p->drawRect(marker_rect);
 
 		if (!name.isEmpty()) {
-			p->setPen(ColorCoding::get_ui_selector_color(
-				ColorCoding::get_color(color)));
+			p->setPen(AppColorCoding::get_ui_selector_color(
+				AppColorCoding::get_color(color)));
 			p->drawText(marker_rect.adjusted(marker_width / 4, 0, 0, 0), name,
 						op);
 		}