feat(07-06): extend SettingsSidebar with Allgemein > SMTP category

- Add 'Allgemein' category section ABOVE existing Dashboard category
- Single SMTP link to /settings/general/smtp with identical active/inactive styling and aria-current
- isActive('/settings/general/smtp') works via pathname.startsWith branch
- Existing Dashboard/Widgets/Calendar items unchanged

apps/web/src/components/settings/settings-sidebar.tsx

@@ -38,6 +38,29 @@ export function SettingsSidebar() {
       role="navigation"
       aria-label={t('navLabel')}
     >
+      {/* Allgemein category — above Dashboard (Surface C, 07-06) */}
+      <div className="p-4 pb-2">
+        <h2 className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">
+          {t('categoryGeneral')}
+        </h2>
+      </div>
+      <nav className="mb-2 flex flex-col gap-1 px-3">
+        <Link
+          href="/settings/general/smtp"
+          className={`flex items-center rounded-md px-2 py-1.5 text-sm transition-colors ${
+            isActive('/settings/general/smtp')
+              ? 'bg-sidebar-accent text-sidebar-accent-foreground font-medium'
+              : 'text-sidebar-foreground hover:bg-muted'
+          }`}
+          aria-current={
+            isActive('/settings/general/smtp') ? 'page' : undefined
+          }
+        >
+          {t('categorySmtp')}
+        </Link>
+      </nav>
+
+      {/* Dashboard category — existing items unchanged */}
       <div className="p-4">
         <h2 className="text-xs font-semibold uppercase tracking-wider text-muted-foreground">
           {t('categoryDashboard')}