fix: patch 11 dependency vulnerabilities

[dcbouius]

Summary

• Ran npm audit fix to resolve 11 of 13 dependency vulnerabilities (5 high, 6 moderate)
• Patched transitive dependencies: minimatch, glob, flatted, picomatch, postcss, brace-expansion, ajv, js-yaml, mdast-util-to-hast, yaml, @eslint/plugin-kit
• 2 remaining moderate issues are a postcss vulnerability bundled inside Next.js — fixing requires downgrading Next.js to 9.x which is not viable

Test plan

• Verify npm install completes without errors
• Verify npm run build succeeds
• Verify npm audit shows only 2 remaining moderate vulnerabilities
• Smoke test the chat UI locally