refactor(ui): migrate spritz ui to typescript build

[onutc]

Summary

• move the static Spritz UI logic into a TypeScript source tree under ui/src
• add a tsdown-based browser build that emits stable assets into ui/dist and update Docker/CI to use it
• make the UI tests run against the built bundles instead of the old source JS files

Validation

• cd /Users/onur/repos/spritz/ui && pnpm build && pnpm typecheck && pnpm test
• cd /Users/onur/repos/spritz && docker build -f ui/Dockerfile -t spritz-ui-ts-test .
• cd /Users/onur/repos/spritz && bash -n ui/entrypoint.sh
• cd /Users/onur/repos/spritz && git diff --check