Pull Request Checklist

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• 🧪 Added tests for changed code.
• 🛠️ All tests pass when run locally (run tox or make test to find out!).
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Description of Changes

Fixes #1170: Correct DST Handling in shift Function

This PR addresses the issue with incorrect daylight saving time (DST) handling when using the shift function in the Arrow library.

Changes:

• Modified the shift function to correctly handle transitions during DST changes.
• Added logic to detect positive or negative offset changes when shifting across DST boundaries.
• Adjusted the behavior during spring-forward (to skip the missing hour) and fall-back (to use the second occurrence of a repeated hour).

Issue Link:

Closes: #1170

Explanation:

Previously, the shift function did not account for the changes in offsets that occur during DST transitions, leading to unexpected behavior when shifting times. This fix ensures that:

• For spring-forward transitions, any shifts that would land in the missing hour are adjusted forward.
• For fall-back transitions, the repeated hour is handled properly by using the fold attribute to select the second occurrence.

Testing:

• Added tests for time shifts that cross DST start and end dates to verify the behavior.
• Ensured consistency when using timedelta shifts and repeated shifts.