Redesign shared browser pages with responsive local assets

[AgentStart1]

Summary

Redesign Feiya's browser file-sharing, login, and messaging pages with a green sidebar layout on desktop and compact top navigation on phones. The file page now exposes loading, empty, failure, and retry states; messaging supports multiline drafts, connection feedback, explicit reconnect, and copying on LAN HTTP. Styles, scripts, and licensed Phosphor icons are bundled locally, removing the pages' CDN dependencies.

Network state and asynchronous work live in a DOM-independent Host inside a dedicated Worker. Draft editing stays synchronous in the page, and reconnecting does not replay messages.

Add explicit routes for /login, /, and /messages, make /web/* available before login, and namespace HTML resources under feiya/. Real-router tests exposed a collision with a dependency's index.html; removing the broad classpath static mapping ensures the intended page is served.

Validation

• :app:testDebugUnitTest: 63 tests passed, including real Ktor HTTP route, session, login, and bundled-resource coverage.
• :app:assembleDebug: passed.
• npm --prefix tests/web test: 6 Host tests passed.
• npm --prefix tests/web run test:browser: Chromium desktop/mobile checks passed for downloads, SSE refresh, empty/error/retry states, long filenames, literal untrusted text, sending/copying, IME input, disconnect/reconnect, invalid passwords, and passwordless login. No page JavaScript errors or external asset requests in the passing run.
• Visual comparison completed against the selected design; development preview and test instructions are in DEVELOPMENT.md.

Browser interaction checks use mock HTTP/SSE/WebSocket endpoints. Ktor routing is tested separately on the JVM. An installed-device end-to-end flow and Alpha/Release builds were not run for this change. No CI workflow changes.