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/common/crashpadinterface.cpp

@@ -0,0 +1,102 @@
+/***
+
+  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 "crashpadinterface.h"
+
+#ifdef USE_CRASHPAD
+
+#include <QCoreApplication>
+#include <QDateTime>
+#include <QDebug>
+#include <QDir>
+#include <QProcess>
+
+#include "crashpadutils.h"
+#include "filefunctions.h"
+
+#if BUILDFLAG(IS_WIN)
+#include <Windows.h>
+#endif
+
+crashpad::CrashpadClient *client;
+
+bool InitializeCrashpad()
+{
+	QString report_path = QDir(olive::FileFunctions::GetTempFilePath())
+							  .filePath(QStringLiteral("reports"));
+
+	QString handler_fn =
+		olive::FileFunctions::GetFormattedExecutableForPlatform(
+			QStringLiteral("crashpad_handler"));
+
+	// Generate absolute path
+	QString handler_abs_path =
+		QDir(QCoreApplication::applicationDirPath()).filePath(handler_fn);
+
+	bool status = false;
+
+	if (QFileInfo::exists(handler_abs_path)) {
+		base::FilePath handler(QSTRING_TO_BASE_STRING(handler_abs_path));
+
+		base::FilePath reports_dir(QSTRING_TO_BASE_STRING(report_path));
+
+		base::FilePath metrics_dir(
+			QSTRING_TO_BASE_STRING(QDir(olive::FileFunctions::GetTempFilePath())
+									   .filePath(QStringLiteral("metrics"))));
+
+		// Metadata that will be posted to the server with the crash report map
+		std::map<std::string, std::string> annotations;
+
+		// Disable crashpad rate limiting so that all crashes have dmp files
+		std::vector<std::string> arguments;
+		arguments.push_back("--no-rate-limit");
+		arguments.push_back("--no-upload-gzip");
+
+		// Initialize Crashpad database
+		std::unique_ptr<crashpad::CrashReportDatabase> database =
+			crashpad::CrashReportDatabase::Initialize(reports_dir);
+		if (database == NULL)
+			return false;
+
+		// Disable automated crash uploads
+		crashpad::Settings *settings = database->GetSettings();
+		if (settings == NULL)
+			return false;
+		settings->SetUploadsEnabled(false);
+
+		// Start crash handler
+		client = new crashpad::CrashpadClient();
+		status = client->StartHandler(
+			handler, reports_dir, metrics_dir,
+			"https://olivevideoeditor.org/crashpad/report.php", annotations,
+			arguments, true, true);
+	}
+
+	// Override Crashpad exception filter with our own
+	if (!status) {
+		qWarning()
+			<< "Failed to start Crashpad, automatic crash reporting will be disabled";
+	}
+
+	return status;
+}
+
+#endif // USE_CRASHPAD