fix(i18n): hardkodierte Strings in DNS/RoutingRules/Settings/Backends bereinigen

- DNS Settings: Loopback/allIPv4/allIPv6 Interface-Labels in t() überführt
- RoutingRules: UP/DOWN-Tags + fehlende onError-Handler in create/update
- Settings: t-Variable-Shadowing in top_tables-Map behoben (t → tbl)
- Backends: 'Live'-Spaltenheader → t('backends.server.live')
- common.up/down + dns.settings.allIPv4/allIPv6/loopback in en+de ergänzt

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

management-ui/src/pages/Settings/index.tsx

@@ -326,8 +326,8 @@ export default function SettingsPage() {
                 {dbSize.top_tables.length > 0 && (
                   <Typography.Text type="secondary" style={{ fontSize: 11 }}>
                     {t('settings.dbSizeTop')}:{' '}
-                    {dbSize.top_tables.slice(0, 3).map(t =>
-                      `${t.name} (${t.human_size})`
+                    {dbSize.top_tables.slice(0, 3).map(tbl =>
+                      `${tbl.name} (${tbl.human_size})`
                     ).join(', ')}
                   </Typography.Text>
                 )}