app: migrate all engine access to the C ABI facade (nm U _ZN5olive = 0)

Every app module now reaches liboakengine exclusively through
oakengine_* C calls, EngineEventBridge subscriptions and app-side
handle headers (cliphandle/keyframehandle/nodevaluehandle/oakvaluehelper).
Direct C++ command construction, engine signal connect()s, and engine
type usage in MOC-visible signatures are gone: 557 -> 0 undefined
olive:: symbols in oak-editor.

app/widget/timebased/timescaledobject.cpp

@@ -26,6 +26,7 @@
 
 #include "audio/audiovisualwaveform.h"
 
+#include "oakengine/node.h"
 namespace olive
 {
 
@@ -34,7 +35,7 @@ const int TimeScaledObject::k_calculate_dimensions_padding = 10;
 TimeScaledObject::TimeScaledObject()
 	: scale_(1.0)
 	, min_scale_(0)
-	, max_scale_(AudioVisualWaveform::k_maximum_sample_rate.to_double())
+	, max_scale_(oakengine_audio_waveform_max_sample_rate())
 {
 }