feat(settings): sidebar submenu nav for settings and xray with icon tabs

Settings and Xray Configs are now expandable sidebar submenus that list their sections; clicking a section opens it via the URL hash (e.g. #general, #basic) and the in-page top tab bar is removed on both pages.

Within each section the collapse groups become horizontal tabs, each with an icon; on mobile only the icon shows with the label in a tooltip, via a shared catTabLabel helper used by both settings and xray.

Subscription Formats: the nested collapses in Fragment/Noises/Mux/Direct are replaced with a cleaner layout - framed field groups, and each noise is a card with a delete button plus a dashed add button.

Xray: the Reset to Default button is now a solid danger button so its hover state is visible.

frontend/src/pages/settings/SubscriptionFormatsTab.css

@@ -1,3 +1,14 @@
-.nested-block {
-  padding: 10px 20px;
+.format-settings {
+  margin-bottom: 8px;
+  border: 1px solid var(--ant-color-border-secondary);
+  border-radius: 8px;
+  overflow: hidden;
+}
+
+.format-settings-list {
+  padding-top: 4px;
+}
+
+.noise-card {
+  margin-bottom: 10px;
 }