Auto forward app return

- performRelay now returns ForwardResult to check success/failure
- After successful auto-forward, navigate back with history.back()
- Early return to skip URL cleanup when leaving the page

Co-authored-by: samuele <samuele@zanca.dev>

- Config view: input for forward URL with save
- Share handler view: displays received content, forward button, status
- Logs view: history of past forwards with status and response
- Mobile-first CSS with tab navigation
- Remove unused logo.svg

- storage.ts: localStorage helpers for config + logs, IndexedDB for share data
- forwarder.ts: POST shared content to configured URL with logging

- Create sw.ts with injectManifest strategy
- Handle POST to /share-target, store data in IndexedDB
- Redirect to app with pending flag

- Install vite-plugin-pwa
- Configure manifest with share_target for POST to /share-target
- Add PWA icons (SVG)
- Update index.html with PWA metadata