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/keyframeview/keyframeviewinputconnection.h

@@ -24,9 +24,12 @@
 
 #include <QObject>
 
+#include "engineeventbridge.h"
 #include "node/node.h"
 #include "node/param.h"
 
+struct OakEngineKeyframe;
+
 namespace olive
 {
 
@@ -85,14 +88,16 @@ private:
 
 	QBrush brush_;
 
+	EngineEventBridge *bridge_ = nullptr;
+
 private slots:
-	void add_keyframe(NodeKeyframe *key);
+	void add_keyframe(OakEngineKeyframe *key);
 
-	void remove_keyframe(NodeKeyframe *key);
+	void remove_keyframe(OakEngineKeyframe *key);
 
-	void keyframe_changed(NodeKeyframe *key);
+	void keyframe_changed(OakEngineKeyframe *key);
 
-	void keyframe_type_changed(NodeKeyframe *key);
+	void keyframe_type_changed(OakEngineKeyframe *key);
 };
 
 }