Changes:
- Added 'Open' button to each plugin in the Installed plugins list
- Clicking Open tries: show_ui(), open(), or get_widget() methods
- Added _open_plugin() method to both PluginsView and PerfectMainWindow
- Added Settings button for plugins that have settings
- Shows error messages if plugin can't be opened
This fixes the issue where plugins couldn't be opened or viewed.
1. Sidebar toggle: Now uses arrows (chevron-right when collapsed, chevron-left when expanded)
2. Dashboard: Quick actions filtered to show only installed plugins
3. Plugins page: New tabs - 'Installed' (enable/disable plugins) and 'Store' (browse/install)
4. Widgets page: Now shows registered widgets from plugins with enable/disable
5. Settings page: Removed Plugin Store and My Plugins tabs (moved to Plugins page)
6. Settings: Changed 'Overlay Opacity' to 'Background Opacity' for clarity
7. Status bar: Shows plugin count, EU window status (Not Running/Running/Focused), version
8. New files: plugins_view.py, widgets_view.py with proper functionality