Setup PWA support (Vite + vite-plugin-pwa) - feature/pwa

[egpennington]

Install and configure vite-plugin-pwa

• Add manifest
• Add icons (192px, 512px)
• Confirm service worker registration

Branch: feature/pwa
Labels: feature, Should Have, Sprint 1

[egpennington]

Install vite-plugin-pwa

Configure registerType: 'autoUpdate', include manifest.json, icons

Test installability on mobile & desktop Chrome