refactor(outbound): probe via xray burstObservatory instead of SOCKS round-trip

Replace the HTTP-mode outbound test that spun up a SOCKS inbound and
ran an httptrace'd request from the Go client with a probe-only xray
config: burstObservatory probes the target outbound directly and the
result is read from xray's /debug/vars metrics endpoint.

The probe lives inside xray, so the measured delay and failure
reasons reflect what xray itself sees over the real proxy chain.
Drops the DNS/Connect/TLS/TTFB breakdown (and statusCode) since the
observatory snapshot only exposes total delay; the frontend popover
is updated accordingly.

frontend/src/pages/xray/OutboundsTab.tsx

@@ -101,10 +101,10 @@ function showSecurity(security?: string): boolean {
   return security === 'tls' || security === 'reality';
 }
 
-function hasBreakdown(r: { endpoints?: unknown[]; ttfbMs?: number; tlsMs?: number; connectMs?: number; dnsMs?: number; statusCode?: number; error?: string } | null | undefined): boolean {
+function hasBreakdown(r: { endpoints?: unknown[]; error?: string } | null | undefined): boolean {
   if (!r) return false;
   if (r.endpoints?.length) return true;
-  return !!(r.ttfbMs || r.tlsMs || r.connectMs || r.dnsMs || r.statusCode || r.error);
+  return !!r.error;
 }
 
 export default function OutboundsTab({
@@ -335,11 +335,6 @@ export default function OutboundsTab({
                   </div>
                   {hasBreakdown(r) && (
                     <>
-                      {r.ttfbMs ? <div>TTFB: {r.ttfbMs} ms</div> : null}
-                      {r.tlsMs ? <div>TLS: {r.tlsMs} ms</div> : null}
-                      {r.connectMs ? <div>Connect: {r.connectMs} ms</div> : null}
-                      {r.dnsMs ? <div>DNS: {r.dnsMs} ms</div> : null}
-                      {r.statusCode ? <div>HTTP {r.statusCode}</div> : null}
                       {(r.endpoints || []).map((ep) => (
                         <div key={ep.address} className="endpoint-row">
                           <span className={ep.success ? 'dot-ok' : 'dot-fail'}>●</span>

frontend/src/schemas/xray.ts

@@ -54,11 +54,6 @@ export const OutboundTestResultSchema = z.object({
   delay: z.number().optional(),
   error: z.string().optional(),
   mode: z.string().optional(),
-  ttfbMs: z.number().optional(),
-  tlsMs: z.number().optional(),
-  connectMs: z.number().optional(),
-  dnsMs: z.number().optional(),
-  statusCode: z.number().optional(),
   endpoints: z
     .array(
       z.object({