Refresh timer visuals and controls

[ethan-CCY]

Summary

• restyle the stopwatch and countdown views with warm sand and matcha themes plus updated water hues
• format timer output as hh:mm:ss.mmm with smaller millisecond styling and translate control labels with new button colors
• remove the right-side panels, tighten layout, and add .gitignore for build artifacts

Testing

• npm run build

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Codex Task