docs: add Presenton dual-lockfile example and verified case study (#527)

[Ayush7614]

Summary

• Adds lockfile-only snapshots under examples/presenton/ from presenton/presenton@493aff5
  • Root: package.json + package-lock.json (93 packages, 1 finding)
  • Electron: electron/package.json + electron/package-lock.json (501 packages, 8 findings)
• Documents verified baseline scan in website/docs/case-studies/presenton.md — 9/9 first-pass fix coverage across both lockfiles
• AI presentation generator coverage with explicit dual-lockfile scope (Python/FastAPI server deps excluded)
• npm audit counts align with CVE Lite on both lockfiles (1 root · 8 electron)
• Bundles logo at website/static/img/presenton-logo.png

Closes #527

Verified scan output

Root (examples/presenton/):

Parsed 93 packages · 1 finding (1 high, transitive axios via @llamaindex/liteparse)
npm update @llamaindex/liteparse — fixes 1/1
npm audit: 1 high

Electron (examples/presenton/electron/):

Parsed 501 packages · 8 findings (5 high · 3 medium · 1 direct uuid)
4 command groups — fixes 8/8
npm audit: 5 high · 3 moderate (8 total)

Test plan

• npm run build
• node dist/index.js examples/presenton --verbose --all
• node dist/index.js examples/presenton/electron --verbose --all
• Case study numbers match live scan JSON
• npm audit run on both lockfiles — counts align with CVE Lite
• Docusaurus site builds (if CI runs on PR)

[Ayush7614]

cc: @sonukapoor