fix(security): close SSRF guard bypasses in ssrfGuard.js (#3714)

Closes four SSRF guard bypasses reported in #3714:
- Block alternate IPv6 encodings (hex format, NAT64, IPv4-compatible, IPv4-mapped) by parsing to 16-bit groups
- Normalize trailing dots on hostnames to prevent FQDN bypasses
- Add assertPublicUrlResolved() with DNS resolution to block wildcard DNS domains resolving to private/metadata IPs
- Add fetchPublic() to safely handle and validate HTTP redirects

open-sse/handlers/search/index.js

@@ -10,6 +10,7 @@
 import { buildSearchRequest } from "./callers.js";
 import { normalizeSearchResponse } from "./normalizers.js";
 import { handleChatSearch } from "./chatSearch.js";
+import { fetchPublic } from "../../../src/shared/utils/ssrfGuard.js";
 
 const GLOBAL_TIMEOUT_MS = 15000;
 const NON_RETRIABLE = new Set([400, 401, 403, 404]);
@@ -100,7 +101,7 @@ async function tryDedicatedProvider({ provider, providerConfig, body, credential
   log?.info?.("SEARCH", `${provider.id} | "${params.query.slice(0, 80)}" | type=${params.searchType}`);
 
   try {
-    const resp = await fetch(url, { ...init, headers: sanitizeHeaders(init.headers), signal: controller.signal });
+    const resp = await fetchPublic(url, { ...init, headers: sanitizeHeaders(init.headers), signal: controller.signal });
     clearTimeout(timer);
     if (!resp.ok) {
       const errText = await resp.text().catch(() => "");