Add brew timer, EN/UA localization, and UI/accuracy improvements for the 4:6 calculator

[inceon]

Summary

This PR improves the 4:6 calculator experience with a guided timer flow, full localization support (including Ukrainian), and corrected pour calculations.

What changed

• Fixed 60% stage pour-splitting so total poured water always matches the computed target (including odd values).
• Added brew timer features:
  • Start / Pause / Reset
  • elapsed clock
  • active step highlighting
  • “Pour now” cue for 3 seconds
  • remove-dripper end cue
• Added optional sound notifications for pour/removal cues.
• Localized all visible UI text and timer messages.
• Added language switcher (EN | UA) as a minimal top-right text control.
• Moved translations to a separate file (src/i18n/translations.js) for cleaner structure.
• Updated method wording/docs in UI content to match intended 4:6 guidance.

Why

• Improve calculation reliability.
• Make brewing flow easier to follow in real time.
• Support multilingual use and cleaner i18n maintenance.

Validation

• npm run lint passes
• npm run build passes

[aeyoll]

Hello @inceon, thx for the PR. This project still uses yarn v1 for deps management, can you remove the package-lock.json please? Thx

[inceon]

Hello @inceon, thx for the PR. This project still uses yarn v1 for deps management, can you remove the package-lock.json please? Thx

Updated 🙂