Prepare repository for open source fund review

[BigCatNotFat]

Summary

• Refresh README, open-source readiness docs, privacy/security docs, package metadata, and repository signals for OSS fund review.
• Add a lightweight Overleaf workflow diagram and align project metadata with the current AGPL-3.0-only, v3.3.7 repository state.
• Add package-lock support and upgrade Vite/esbuild-related dev tooling to clear high-severity audit findings.
• Fix narrow TypeScript configuration/declaration issues so the existing CI typecheck passes.

Validation

• npm ci
• npm run build
• npx tsc --noEmit --pretty false
• npm audit --audit-level=high