Limit request sizes, answer 413, stop cleanly on SIGTERM

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaC9HmtHMdRP8dAbN4wAKj

auth.js

@@ -144,7 +144,7 @@ const rp = req => {
 };
 const equalStr = (a, b) => { const x = Buffer.from(String(a)), y = Buffer.from(String(b)); return x.length === y.length && crypto.timingSafeEqual(x, y); };
 
-const readBody = req => new Promise((ok, no) => { const c = []; req.on('data', d => c.push(d)); req.on('end', () => ok(Buffer.concat(c).toString())); req.on('error', no); });
+const { readBody } = require('./body');
 const send = (res, code, obj) => { res.writeHead(code, { 'content-type': 'application/json', ...(res.getHeader('Set-Cookie') ? { 'Set-Cookie': res.getHeader('Set-Cookie') } : {}) }); res.end(JSON.stringify(obj)); };
 const credsOf = uid => store.creds.filter(c => c.uid === uid);