fix(security): scope OAuth callback postMessage targets and re-enable TLS verification on DNS-bypass fetch (#998)

Two findings, neither blocked by anything else:

1. src/app/callback/page.js — the OAuth callback page posted the
   { code, state } payload to window.opener with targetOrigin "*", so any
   page that opened the popup against the well-known redirect_uri received
   the live OAuth code. The expectedOrigins list was already computed but
   never used. Iterate over it and pass the origin per send.

2. open-sse/utils/proxyFetch.js — createBypassRequest() set
   rejectUnauthorized: false on the HTTPS request that runs after the
   Google-DNS-resolved real-IP fallback (used for cloudcode-pa.googleapis,
   GitHub Copilot, Cursor, AWS LLM endpoints). Combined with servername:
   parsedUrl.hostname this gave SNI-correct connections that nonetheless
   ignored cert validation, so an on-path attacker could swap in their
   own cert and read the user's API tokens / prompts. Drop the flag.

Detected by Aeon + semgrep (javascript.browser.security.wildcard-postmessage-configuration
+ problem-based-packs.insecure-transport.js-node.bypass-tls-verification).
Severity: HIGH (#1) / MEDIUM (#2).
CWEs: CWE-1385 (#1), CWE-295 (#2).

Co-authored-by: aeonframework <aeon@aeonframework.dev>

open-sse/utils/proxyFetch.js

@@ -155,8 +155,13 @@ async function createBypassRequest(parsedUrl, realIP, options) {
     socket.connect(HTTPS_PORT, realIP, () => {
       const reqOptions = {
         socket,
+        // SNI + cert hostname are validated against the hostname the caller
+        // asked for, not the IP we connected to. This keeps the DNS-bypass
+        // (avoiding /etc/hosts MITM) while still rejecting on-path attackers
+        // that present a different cert. The MITM_BYPASS_HOSTS targets are
+        // all public-CA-issued (Google / GitHub / AWS / Cursor) so default
+        // verification works without any extra trust store.
         servername: parsedUrl.hostname,
-        rejectUnauthorized: false,
         path: parsedUrl.pathname + parsedUrl.search,
         method: options.method || "POST",
         headers: {