Introduces optional 'categories' and 'authors' fields to plugin manifests, updates plugin-manager.js to normalize and expose these fields, and enhances the settings UI to display plugin tags and authors. Also updates documentation and an example plugin manifest to demonstrate the new fields.
Introduces a plugin architecture, including a PluginManager, plugin loading in main and renderer processes, and a sample plugin demonstrating menu, IPC, and context menu contributions. Adds a Plugins tab to the settings UI for managing plugins (enable/disable, reload), and updates preload.js to load renderer preloads from plugins. Documentation for plugin development is included in README-PLUGINS.md.
andrew