fix(security): harden auth reset, rate limiter fallback, and CI secrets

- Move CI_AUTH_SECRET from plaintext to ${{ secrets.CI_AUTH_SECRET }}
- Wrap password reset (update + session kill + token mark) in $transaction
  to prevent stale sessions on partial failure (CWE-613)
- Rate limiter Redis fallback now uses stricter degraded limits
  (maxRequests/10) and logs at error level instead of warn

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -14,7 +14,7 @@ env:
   NODE_VERSION: "20"
   PNPM_VERSION: "9.14.2"
   CI_AUTH_URL: http://localhost:3100
-  CI_AUTH_SECRET: capakraken-ci-build-secret-rotate-if-shared
+  CI_AUTH_SECRET: ${{ secrets.CI_AUTH_SECRET }}
 
 jobs:
   guardrails: