Release quoin-ui 0.4.0 with Solid 2 RC support#3

Summary

• bump quoin-ui to 0.4.0 and move the Solid runtime/compiler peers to 2.0.0-rc.1
• replace the legacy Vite wrapper with @solidjs/vite-plugin
• adapt SSR qualification to the RC's synchronous renderToString API and keep Avatar image probing browser-only
• rebase and document the remaining createContext development-build patch for RC.1

Qualification

• bun biome check .
• bun run typecheck
• bun run test — 1,892 pass, 0 fail
• bun run test:prod — 1,892 pass, 0 fail
• bun run test:ssr — 38 pass, 0 fail
• bun run test:hydration — 11 pass, 0 fail
• bun run verify:ssr — 42 server entries imported, 2 rendered
• bun run demo:build
• bun run verify:pack — all 42 runtime/type entrypoints pass from the packed 0.4.0 tarball

Real-browser qualification was intentionally skipped for this PR.