feat(render): dynamic OpenGL/Vulkan backend split and backend-neutral viewer

- Extract libolive-rendercore static library to minimize backend link boundary.
- Add DynamicRenderer adapter with C ABI (oakgl/oakvulkan shared libs).
- Make OAK_ENABLE_DYNAMIC_RENDER_BACKEND default ON with OpenGL fallback.
- Implement VulkanRenderer prototype (textures, shaders, UBO blit, readback).
- Add backend-neutral viewer readback path (offscreen -> QImage -> QPainter).
- Refactor PluginRenderer to be renderer-agnostic; OFX plugins fall back to CPU
  path on non-OpenGL backends while preserving OpenGL render path.
- Add Renderer::AttachOutputTexture/DetachOutputTexture and C ABI forwards.
- Update docs/zh/render-backend-dynamic-plan.md for Phase 3/4/5.

app/common/avframeptr.h

@@ -0,0 +1,48 @@
+/***
+
+  Olive - Non-Linear Video Editor
+  Copyright (C) 2022 Olive Team
+  Modifications Copyright (C) 2025 mikesolar
+
+  This program is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+***/
+
+#ifndef AVFRAMEPTR_H
+#define AVFRAMEPTR_H
+
+extern "C" {
+#include <libavutil/frame.h>
+}
+
+#include <memory>
+
+namespace olive
+{
+
+using AVFramePtr = std::shared_ptr<AVFrame>;
+
+inline AVFramePtr CreateAVFramePtr(AVFrame *f)
+{
+	return std::shared_ptr<AVFrame>(f, [](AVFrame *g) { av_frame_free(&g); });
+}
+
+inline AVFramePtr CreateAVFramePtr()
+{
+	return CreateAVFramePtr(av_frame_alloc());
+}
+
+}
+
+#endif // AVFRAMEPTR_H

app/common/ffmpegutils.h

@@ -30,6 +30,7 @@ extern "C" {
 
 #include <olive/core/core.h>
 
+#include "common/avframeptr.h"
 #include "render/videoparams.h"
 
 namespace olive
@@ -85,16 +86,6 @@ public:
 	static AVPixelFormat ConvertJPEGSpaceToRegularSpace(AVPixelFormat f);
 };
 
-using AVFramePtr = std::shared_ptr<AVFrame>;
-inline AVFramePtr CreateAVFramePtr(AVFrame *f)
-{
- 	return std::shared_ptr<AVFrame>(f, [](AVFrame *g) { av_frame_free(&g); });
-}
-inline AVFramePtr CreateAVFramePtr()
-{
-	return CreateAVFramePtr(av_frame_alloc());
-}
-
 }
 
 #endif // FFMPEGABSTRACTION_H