chore(deps): fix security audit findings (backend 33→22 incl. critical, frontend 40→0)

[tongshu2023]

Summary

Works through the automated security audit findings from #138 (and the earlier weekly issues #135/#134/#133).

Backend: 33 → 22 advisories (critical eliminated) · Frontend: 40 → 0

Backend (npm audit fix --legacy-peer-deps)

• Clears the critical protobufjs advisory and 4 highs (fast-xml-parser/fast-xml-builder, @xmldom/xmldom, underscore, cacache chains) plus assorted moderates — all within existing semver ranges.
• --legacy-peer-deps matches the repo's current install reality: the lockfile already contains an openai@6 vs @browserbasehq/stagehand (openai@^4 peer) conflict that a strict npm install refuses to resolve.
• Verified: npm run build (tsc) clean.

The 22 that remain need maintainer decisions

1. @keyv/sqlite → sqlite3 chain (9 advisories, all install-time) — sqlite3@5.1.7 is the final release of an unmaintained package; the node-gyp/tar/make-fetch-happen advisories live in its build toolchain, not the runtime. Options: switch the Keyv store to better-sqlite3-based storage, or accept the risk as install-time-only.
2. LangChain 0.3 → 1.x (13 advisories incl. the langsmith highs) — a real API migration, too invasive to bundle into an audit PR. Happy to attempt it as a separate PR if wanted.

Frontend

• pnpm update within existing semver ranges clears 39 of 40 (react-router XSS/DoS series, minimatch/picomatch ReDoS, flatted, postcss, rollup, etc.).
• The last one — critical shell-quote 1.8.3 — is exactly pinned by concurrently@9.x, so concurrently is bumped 9 → 10 (dev-only script runner; v10 ships shell-quote 1.8.4).
• Verified: pnpm run build (tsc + vite) clean.

Verification

• Backend: npm run build exit 0
• Frontend: pnpm audit → "No known vulnerabilities found"; pnpm run build exit 0

[tongshu2023]

Two follow-up commits after watching CI:

1. a68dd47 — .npmrc with legacy-peer-deps=true: the "Validate Code" job was failing in npm install on a pre-existing openai@6 vs @browserbasehq/stagehand (peer openai@^4) ERESOLVE conflict — the same reason the pipeline fails intermittently on main. With the .npmrc, installs are deterministic for CI and contributors; Validate Code now passes.
2. d132770 — toolchain overrides: sqlite3@5.1.7 (final release of an unmaintained package) pulls node-gyp@8 with vulnerable tar/cacache/make-fetch-happen. Pinning those to patched versions clears 6 of the 7 remaining highs. sqlite3 installs via prebuilt binaries, so the node-gyp bump only affects the source-build fallback.

Backend now: 33 → 10 (1 high + 9 moderate) — everything left sits behind the LangChain 0.3 → 1.x migration (incl. the langsmith advisories, whose patched releases require langchain 1.x-era APIs; force-overriding it against @langchain/core@0.3 would risk runtime breakage, so I left it for a dedicated migration PR).

Remaining CI reds are environmental: the "Dependency Vulnerability Check" gate (npm audit --audit-level=high) will stay red until the langchain migration lands (it's red on main too), and the Docker job failed on a registry-1.docker.io timeout — worth a re-run.