refactor: remove unused result-batches.ts and migrate manual formatting to Format singleton (@codewithyuvraj24)

[codewithyuvraj24]

Changes

1. Delete unused result-batches.ts

• frontend/src/ts/elements/result-batches.ts was not imported or referenced anywhere in the codebase.
• The file itself contained a //TODO fix or delete? comment.

2. Migrate manual formatting in result.ts to use Format singleton

• Addressed the //TODO: use Format comment at the top of result.ts.
• Replaced manual .toFixed(2) and Numbers.roundTo2(...).toFixed(2) calls with Format.decimals() for WPM, raw WPM, test duration, and personal best annotations.

3. Clean up route-controller.ts

• Removed commented-out event?.preventDefault() and its //todo: figure out if this was ever used comment. The navigate function has no event parameter, so this was dead code.

Verification

• Ran pnpm oxlint --type-aware --type-check — passed with 0 errors.
• Ran local dev server (pnpm dev-fe) — compiles and starts successfully.

[fehmer]

this needs to be converted to solidjs