fix: update Vite security dependencies

[palvimaki]

Summary

• Update Vite from 8.0.12 to 8.2.2.
• Resolve nanoid 3.3.18 and postcss 8.5.26.
• Remove all npm audit findings.

Verification

• npm test — 20 files and 83 tests passed.
• npm run build — passed.
• npm audit — 0 findings.
• Kimi security review — VERDICT: GO.

Note

• The repository defines no lint script or lint configuration. The build runs tsc --noEmit successfully.