style(settings): fold the Happ settings into four tabs

Seven tabs, several holding one or two settings, made the page hard to
scan. The encrypted-links switch moves above the tabs under
auto-detection, the colour profile joins the banners under Appearance &
Theme, and Android per-app proxy joins Network & TUN Engine. The QR
modal's settings link no longer needs a happTab selector, and the three
orphaned tab-label keys are dropped from every locale.

frontend/src/test/client-qr-modal.test.tsx

@@ -241,7 +241,7 @@ describe('ClientQrModal Happ presentation', () => {
     expect(view.onOpenChange).toHaveBeenCalledOnce();
     expect(view.onOpenChange).toHaveBeenCalledWith(false);
     expect(screen.getByTestId('location').textContent).toBe(
-      '/settings?subscriptionTab=happ&happTab=links#subscription',
+      '/settings?subscriptionTab=happ#subscription',
     );
     expect(HttpUtil.post).not.toHaveBeenCalled();
   });