Fix plugin lifecycle, tabs cleanup, and add auto-scroll to tabs

- Fix unload() method naming in nanoesq_temp_buffer plugin
- Wrap tabs_widget in ScrolledWindow/Viewport for proper scrolling
- Add auto-scroll to center when switching/adding tabs
- Return manifest_meta in manifest_manager for manual plugins
- Refactor remove_plugin() to properly clean up all manifest lists
- Fix widget references in plugins_ui for proper removal

plugins/code/commands/nanoesq_temp_buffer/plugin.py

@@ -23,7 +23,7 @@ class Plugin(PluginCode):
     def load(self):
         self._manage_signals("register_command")
 
-    def load(self):
+    def unload(self):
         self._manage_signals("unregister_command")
 
     def _manage_signals(self, action: str):