feat(inbounds): add Real client IP presets to capture visitor IP behind CDN/relay

Surface the existing sockopt knobs (acceptProxyProtocol, trustedXForwardedFor) as a guided 'Real client IP' preset selector in the inbound form, so the real visitor IP is recovered behind Cloudflare CDN or an L4 tunnel/relay instead of recording the intermediary address. Presets are mutually exclusive, warn on incompatible transports, and add tooltips, docs, and translations for all locales.

frontend/src/test/inbound-form-blocks.test.tsx

@@ -89,7 +89,7 @@ describe('inbound transport forms', () => {
 
   it('SockoptForm field structure is stable (enabled + happy eyeballs)', () => {
     renderInForm(
-      () => <SockoptForm toggleSockopt={noop} />,
+      () => <SockoptForm toggleSockopt={noop} network="tcp" />,
       { streamSettings: { sockopt: { happyEyeballs: {} } } },
     );
     expect(fieldLabels()).toMatchSnapshot();