build: split the engine into liboakengine.so; worker drops the UI entirely

Physical split: app/{audio,cli,codec,common,config,node,pluginSupport,
render,task,timeline,undo,tool,shaders} plus coreengine, version and
ui/icons+colorcoding move to a new top-level engine/ tree, built as
liboakengine.so (shared). The render backends (oakgl/oakvulkan) move
with it and link the engine library instead of embedding a static
render-core subset (libolive-rendercore is gone).

- oak-render-worker now links liboakengine instead of the whole
  libolive-editor object set: 336MB -> 2.9MB, no Qt Widgets UI
- the editor links liboakengine for the engine and keeps only UI
  objects in libolive-editor
- install/packaging: GNUInstallDirs libdir on Linux, bundle copy on
  macOS, oakengine.dll staged for NSIS, AppImage validation entry
- fix backend lookup for the new layout: DynamicRenderer searched
  ../app but backends now live in engine/; a stale pre-split liboakgl
  in the build tree got dlopened instead, re-initialized and later
  destroyed the interposed engine statics (full-suite segfault at
  DialogSequenceParameterTab, found via gdb watchpoint)

engine/render/interlacetexture.cpp

@@ -0,0 +1,59 @@
+/***
+
+  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/>.
+
+***/
+
+#include "renderer.h"
+
+#include "common/filefunctions.h"
+#include "node/value.h"
+#include "render/job/shaderjob.h"
+
+namespace olive
+{
+
+TexturePtr Renderer::interlace_texture(TexturePtr top, TexturePtr bottom,
+									  const VideoParams &params)
+{
+	color_cache_mutex_.lock();
+	if (interlace_texture_.isNull()) {
+		interlace_texture_ =
+			create_native_shader(ShaderCode(FileFunctions::read_file_as_string(
+				QStringLiteral(":/shaders/interlace.frag"))));
+	}
+	color_cache_mutex_.unlock();
+
+	ShaderJob job;
+	job.insert(QStringLiteral("top_tex_in"),
+			   NodeValue(NodeValue::k_texture, QVariant::fromValue(top)));
+	job.insert(QStringLiteral("bottom_tex_in"),
+			   NodeValue(NodeValue::k_texture, QVariant::fromValue(bottom)));
+	job.insert(QStringLiteral("resolution_in"),
+			   NodeValue(NodeValue::k_vec2,
+						 QVector2D(params.effective_width(),
+								   params.effective_height())));
+
+	TexturePtr output = create_texture(params);
+
+	blit_to_texture(interlace_texture_, job, output.get());
+
+	return output;
+}
+
+}