Centralize legacy document canvas bridge

src/legacy_document_canvas_services.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "app_core/document_canvas.h"
+#include "app_core/document_resize.h"
+#include "foundation/result.h"
+
+class App;
+
+namespace pp::panopainter {
+
+[[nodiscard]] bool legacy_document_canvas_available(const App& app) noexcept;
+[[nodiscard]] pp::foundation::Status execute_legacy_document_canvas_clear_plan(
+    App& app,
+    const pp::app::DocumentCanvasClearPlan& plan);
+[[nodiscard]] pp::foundation::Status execute_legacy_document_resize_plan(
+    App& app,
+    const pp::app::DocumentResizePlan& plan);
+
+} // namespace pp::panopainter