Fix timezone handling for Borg 2.x archive timestamps (#2390)

[mr-raj12]

Description

Convert Borg 2.x UTC timestamps to local time before storing as naive datetimes.
Borg 2.x returns timestamps with UTC timezone info (e.g., 2018-11-06T14:24:04+00:00). The old code stripped timezone with .replace(tzinfo=None), storing
raw UTC values that displayed incorrectly as local time in the UI.

Changes (2 files):

File	Change
src/vorta/borg/create.py:25	Add .astimezone() before .replace(tzinfo=None)
src/vorta/borg/list_repo.py:57	Same fix

Behavior:

• Borg 1.x (naive timestamps): No change — .astimezone() on naive datetime assumes local time
• Borg 2.x (UTC timestamps): Now correctly converts UTC → local before storing

Related Issue

Closes #2390

Motivation and Context

Users in non-UTC timezones would see incorrect archive times when using Borg 2.x. A backup made at 9:24 AM local (EST) would display as "14:24" (the raw UTC
value).

How Has This Been Tested?

• Verified datetime behavior for both Borg 1.x and 2.x timestamp formats
• Ruff lint passes
• Unit tests pass (4 passed, 5 skipped on Windows)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have read the CONTRIBUTING guide.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

I provide my contribution under the terms of the license of this repository and I affirm the Developer Certificate of Origin.