Replace the top icon-button bar in SettingsView with a grouped left
QTreeWidget: Application, Cards & Data, Chat & Sound, Advanced. The
active page is the selected row (palette highlight); search mode hides
the tree; group headers expand but never select. Page tr() contexts
stay DlgSettings; new group names are SettingsView strings.
Take over DlgSettings::updateLanguage: swap the QTranslator on
langChanged before any retranslateUi runs, so picking a language
applies immediately instead of waiting for a restart.
Move the search bar, tab bar, stacked pages and search results out of
DlgSettings into a reusable SettingsView widget. The dialog becomes a
thin frame (title, OK button, close validation) delegating to the view.
No visual or behavior change; tr() contexts preserved as DlgSettings.
