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/timelinewidget/tool/rolling.cpp

@@ -22,7 +22,6 @@
 #include "widget/timelinewidget/timelinewidget.h"
 
 #include "node/block/gap/gap.h"
-#include "node/nodeundo.h"
 #include "rolling.h"
 
 namespace olive