Improve tool discovery and responsive UX

[1337lean]

Summary

• promote tool search into the hero and group networking tools by task
• add a mobile navigation menu and move the IP Lens promotion after networking tools
• label tools by local, browser, server, or worker execution path
• improve launcher focus trapping, opener restoration, keyboard state, and scroll locking
• increase small-text legibility and reserve external-link arrows for external destinations
• add a branded 1200x630 social preview with updated Open Graph metadata
• preserve and integrate the latest SEO content and structured metadata from main

Validation

• npm run lint
• npm run typecheck
• npm test (45 tests)
• npm run build
• production Docker image build
• Docker smoke checks for the homepage, local and server-backed tool pages, tool social images, IP Lens, and the new social preview asset