feat(outbound): batched connection tester with direct timed HTTP probes

Replace the per-outbound burstObservatory polling (one temp xray spawn +
up to 15s of /debug/vars polling per outbound, serialised) with one
shared temp xray instance per batch: every tested outbound gets its own
loopback SOCKS inbound plus an inboundTag->outboundTag routing rule, and
the panel times a real HTTP request through each one in parallel. The
probe returns as soon as the response lands and records the HTTP status
plus an httptrace breakdown (proxy connect / TLS via outbound / first
byte) shown in the result popover.

New POST /panel/api/xray/testOutbounds endpoint (array in, results in
input order, max 50); the legacy /testOutbound endpoint now delegates to
the same engine. Test All chunks HTTP probes 16 per request, and a batch
whose shared process never comes up (one structurally-broken outbound
poisons the config) retries each item in an isolated instance so the
broken outbound reports xray's real error while the rest still test.

frontend/src/schemas/xray.ts

@@ -56,10 +56,18 @@ export const OutboundTrafficRowSchema = z.object({
 export const OutboundTrafficListSchema = z.array(OutboundTrafficRowSchema);
 
 export const OutboundTestResultSchema = z.object({
+  tag: z.string().optional(),
   success: z.boolean(),
   delay: z.number().optional(),
   error: z.string().optional(),
   mode: z.string().optional(),
+  // HTTP-mode extras: status answered by the test URL plus the httptrace
+  // timing breakdown (dial to local inbound / target TLS via the outbound /
+  // time to first byte).
+  httpStatus: z.number().optional(),
+  connectMs: z.number().optional(),
+  tlsMs: z.number().optional(),
+  ttfbMs: z.number().optional(),
   endpoints: z
     .array(
       z.object({
@@ -72,6 +80,9 @@ export const OutboundTestResultSchema = z.object({
     .optional(),
 }).loose();
 
+// Batch results from /xray/testOutbounds, aligned with the request order.
+export const OutboundTestResultListSchema = z.array(OutboundTestResultSchema);
+
 export const RuleFormSchema = z.object({
   domain: z.string(),
   ip: z.string(),