feat: refine OAuth proxy controls and quota UI (#433)

* feat: refine oauth management proxy controls

* fix: preserve oauth refresh state and tighten oauth rate limiting

* fix: satisfy codeql oauth rate limiting

* fix: address oauth review comments

* fix: move oauth sensitive limits into prehandlers

* fix: cap oauth quota refresh batch size

package.json

@@ -86,6 +86,7 @@
     "node-cron": "^4.2.1",
     "nodemailer": "^8.0.4",
     "pg": "^8.16.3",
+    "rate-limiter-flexible": "^11.0.0",
     "socks": "^2.8.7",
     "undici": "^6.24.1",
     "ws": "^8.20.0",