fix: honor calendarStartDay when navigating with the End key

[balajis-qb]

Summary

Fixes #6326.

Problem

The calendar lets you jump to the first day of the week with the Home key and to the last day of the week with the End key. When weeks are configured to start on a day other than Sunday (for example calendarStartDay={1} for a Monday–Sunday week), Home respected that setting but End did not.

The cause: the Home handler passed locale and calendarStartDay to getStartOfWeek, but the End handler called getEndOfWeek(date) with no configuration, so date-fns fell back to its own default of a Sunday–Saturday week.

Example — with calendarStartDay={1}, focus on Wednesday, June 12, 2024:

Key	Before	After
Home	Mon, Jun 10 ✅	Mon, Jun 10 ✅
End	Sat, Jun 15 ❌	Sun, Jun 16 ✅

The keyboard handler before the fix:

case KeyType.Home:
  newCalculatedDate = getStartOfWeek(date, locale, calendarStartDay);
  break;
case KeyType.End:
  newCalculatedDate = getEndOfWeek(date); // locale + calendarStartDay dropped
  break;

Changes

• src/date_utils.ts: getEndOfWeek now accepts optional locale and calendarStartDay arguments, mirroring getStartOfWeek, and forwards them to date-fns endOfWeek via { locale, weekStartsOn }.
• src/index.tsx: the End case in the keyboard handler now calls getEndOfWeek(date, locale, calendarStartDay), so Home and End compute symmetric week boundaries.
• src/test/date_utils_test.test.ts: new getEndOfWeek tests — default Sunday–Saturday week, Monday–Sunday week via calendarStartDay, and symmetry with getStartOfWeek.
• src/test/datepicker_test.test.tsx: new test asserting End moves focus to Sunday, June 16, 2024 with calendarStartDay={1}.

The new parameters are optional, so existing single-argument callers and tests are unaffected. yarn test:ci (43 suites, 1489 tests), yarn type-check, and yarn eslint all pass.

Contribution checklist

• I have followed the contributing guidelines.
• I have added sufficient test coverage for my changes.
• I have formatted my code with Prettier and checked for linting issues with ESLint for code readability.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.32%. Comparing base (548a1f3) to head (9c4bba5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6327      +/-   ##
==========================================
+ Coverage   99.29%   99.32%   +0.02%     
==========================================
  Files          30       30              
  Lines        3822     3826       +4     
  Branches     1648     1651       +3     
==========================================
+ Hits         3795     3800       +5     
+ Misses         26       25       -1     
  Partials        1        1              

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