Bugfix: DatePicker DST Offset Handling

[fhasse95]

While testing the DatePicker, I noticed that the selected date could shift during Daylight Saving Time (DST) transitions, resulting in an incorrect date being returned. The reason for this issue is that time zone offsets were applied manually when converting between date values and the millisecond representation used by the Android DatePicker.

To reproduce the issue, you can use the DatePickerPlayground in Skip Showcase. For example, in Germany, selecting dates around the DST transition results in the previous day being returned:

As shown in the screenshot, selecting March 30th still returns the correct value. However, selecting March 29th returns March 28th instead. The same one-day shift can also be observed for earlier dates, such as March 28th and March 27th, indicating that the timezone offset calculation causes dates before the DST transition to be shifted back by one day.

This PR removes the manual offset adjustment and uses direct timestamp conversion instead, ensuring that the selected date is preserved correctly regardless of DST or timezone offsets.

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• AI was used to generate or assist with generating this PR. Please specify below how you used AI to help you, and what steps you have taken to manually verify the changes.

Codex was used to investigate and implement the fix for the DST-related DatePicker issue. After reviewing the proposed changes, I manually verified the fix by testing date selection across different dates and DST boundaries on Android.

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