fix(gateway): WebSocket 同源/loopback 等价放行，修复生产同源跨源 403

后端 go:embed 自服务前端时，页面 origin 与网关 Host 一致（production 模式），
但不在 dev 阶段 ALLOWED_ORIGINS（5173/3000）白名单内，originChecker 记 403
导致 WS /ws/chat 握手失败。

改为：同源（origin host == request host）及 loopback 别名（localhost<->127.0.0.1）
自动放行；跨源（不同主机名）仍走白名单。安全不降级：跨源非白名单依旧拒绝。
新增 TestOriginCheckerSameHost 覆盖同源/loopback等效/跨源拒绝/同主机异端口。

internal/services/gateway/ws_hub.go

@@ -367,8 +367,14 @@ func rawData(d json.RawMessage) any {
 	return d
 }
 
-// originChecker allows same-origin (empty) and whitelisted WebSocket origins,
-// mirroring the CORS allow list. A "*" default allows all.
+// originChecker allows same-origin, same-host, and whitelisted WebSocket origins,
+// mirroring the CORS allow list. A "*" allows all.
+//
+// Same-host relaxation: when cyrene serves its own embedded frontend (production
+// mode), the page origin is exactly the gateway's Host (e.g. http://localhost:10942),
+// which is not in the dev-phase ALLOWED_ORIGINS list. We must let that through so a
+// user who changes PORT does not need to edit .env for the WS to connect. Only truly
+// cross-origin clients (external IM / dashboards on another origin) hit the allow-list.
 func originChecker(allowed map[string]bool, allowAll bool) func(*http.Request) bool {
 	return func(r *http.Request) bool {
 		origin := r.Header.Get("Origin")
@@ -378,6 +384,52 @@ func originChecker(allowed map[string]bool, allowAll bool) func(*http.Request) b
 		if allowAll {
 			return true
 		}
-		return allowed[origin]
+		if allowed[origin] {
+			return true
+		}
+		// Same-host: the Origin matches this request's Host (scheme://host:port == host[:port]).
+		return sameOriginAsHost(origin, r)
 	}
 }
+
+// sameOriginAsHost reports whether origin (a full URL origin string such as
+// "http://localhost:10942") corresponds to this request's Host header. It compares
+// the host[:port] portion with loopback equivalence: "localhost" and "127.0.0.1"
+// (and the IPv6 form) are treated as the same host, so serving the embedded frontend
+// on 127.0.0.1 while a client connects via localhost (or vice versa) still passes.
+func sameOriginAsHost(origin string, r *http.Request) bool {
+	if origin == "" || r == nil {
+		return false
+	}
+	after := origin
+	if i := strings.Index(after, "://"); i >= 0 {
+		after = after[i+3:]
+	}
+	if i := strings.IndexByte(after, '/'); i >= 0 {
+		after = after[:i]
+	}
+	return hostEquivalent(after, r.Host)
+}
+
+// hostEquivalent compares two host[:port] strings, treating empty-port variants,
+// case, and loopback aliases as equal. It handles "localhost" vs "127.0.0.1" and
+// bracketed IPv6 loopback "[::1]".
+func hostEquivalent(a, b string) bool {
+	na := normalizeHost(a)
+	nb := normalizeHost(b)
+	if na == nb {
+		return true
+	}
+	// Loopback aliases: localhost, 127.0.0.1, [::1]
+	loop := map[string]bool{"localhost": true, "127.0.0.1": true, "[::1]": true, "::1": true, "127.0.0.2": true}
+	return loop[na] && loop[nb]
+}
+
+// normalizeHost strips the port (if present), lowercases, and trims brackets.
+func normalizeHost(h string) string {
+	h = strings.ToLower(strings.TrimSpace(h))
+	if i := strings.LastIndex(h, ":"); i >= 0 && !strings.Contains(h[i:], "]") {
+		h = h[:i]
+	}
+	return strings.TrimPrefix(strings.TrimSuffix(h, "]"), "[")
+}