refactor: invert the last engine-to-UI dependencies

- NodeFactory's menu creation moves to UI-side widget/menu/factorymenu
  (the factory only exposes its node library read-only now)
- DiskManager's cache-settings dialog is created through a registered
  std::function handler (registered by Core at startup)
- OlivePluginInstance creates progress UIs through a
  PluginProgressReporter interface (Null fallback headless) and queries
  the active viewer through a provider callback, both registered by Core
- factory.h, diskmanager and pluginSupport no longer reference any
  widget//dialog//panel//window headers or classes

app/pluginSupport/pluginprogressreporter.cpp

@@ -0,0 +1,69 @@
+/*
+ * Oak Video Editor - Non-Linear Video Editor
+ * Copyright (C) 2025 Olive CE Team
+ *
+ * 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 "pluginprogressreporter.h"
+
+namespace olive
+{
+namespace plugin
+{
+namespace
+{
+
+/**
+ * @brief No-op reporter used when no UI factory is registered
+ *
+ * Never emits cancelled(), so processing always continues.
+ */
+class NullPluginProgressReporter : public PluginProgressReporter {
+public:
+	void set_progress(double value) override
+	{
+		(void)value;
+	}
+
+	void show() override
+	{
+	}
+
+	void close() override
+	{
+	}
+};
+
+PluginProgressReporterFactory reporter_factory_;
+
+}
+
+void set_plugin_progress_reporter_factory(
+	PluginProgressReporterFactory factory)
+{
+	reporter_factory_ = std::move(factory);
+}
+
+PluginProgressReporter *
+create_plugin_progress_reporter(const QString &message, const QString &title)
+{
+	if (reporter_factory_) {
+		return reporter_factory_(message, title);
+	}
+
+	return new NullPluginProgressReporter();
+}
+
+}
+}