feat(web): make settings tabs URL-addressable via ?tab=

Add an optional `tab` search param (validated against the known tab set)
to /dashboard/settings and drive the Tabs component from it, so each tab
is shareable/bookmarkable (e.g. /dashboard/settings?tab=referral). Tab
clicks update the URL with replace to avoid history spam; existing links
need no search param since `tab` is optional.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/routes/dashboard/settings.tsx

@@ -8,11 +8,31 @@ const SettingsContent = lazy(() =>
   })),
 );
 
+export const SETTINGS_TABS = [
+  "profile",
+  "security",
+  "connections",
+  "referral",
+  "account",
+  "changelog",
+] as const;
+export type SettingsTab = (typeof SETTINGS_TABS)[number];
+
+function isSettingsTab(value: unknown): value is SettingsTab {
+  return SETTINGS_TABS.includes(value as SettingsTab);
+}
+
 export const Route = createFileRoute("/dashboard/settings")({
+  // `tab` is optional so existing <Link to="/dashboard/settings"> need no search param.
+  validateSearch: (search: Record<string, unknown>): { tab?: SettingsTab } =>
+    isSettingsTab(search.tab) ? { tab: search.tab } : {},
   component: SettingsPage,
 });
 
 function SettingsPage() {
+  const { tab } = Route.useSearch();
+  const navigate = Route.useNavigate();
+
   return (
     <Suspense
       fallback={
@@ -23,7 +43,10 @@ function SettingsPage() {
         </div>
       }
     >
-      <SettingsContent />
+      <SettingsContent
+        tab={tab ?? "profile"}
+        onTabChange={(next) => navigate({ search: { tab: next as SettingsTab }, replace: true })}
+      />
     </Suspense>
   );
 }