fix: fix Application UI using UTC time

[cin-cris]

Description

• Before, the time in the name of new conversation is follow UTC+0 no matter where user is. So I use tzlocal library to get the local machine's time to change in the name.
• Fixes [BUG] Minor bug: Application UI time using UTF time instead of system time #262

Type of change

• New features (non-breaking change).
• Bug fix (non-breaking change).
• Breaking change (fix or feature that would cause existing functionality not to work as expected).

Checklist

• I have performed a self-review of my code.
• I have added thorough tests if it is a core feature.
• There is a reference to the original bug report and related work.
• I have commented on my code, particularly in hard-to-understand areas.
• The feature is well documented.

[taprosoft]

@cin-cris please also update the date_created field on various place https://github.com/search?q=repo%3ACinnamon%2Fkotaemon%20date_created&type=code

Notably
libs/ktem/ktem/db/base_models.py
libs/ktem/ktem/index/file/index.py

[cin-cris]

@taprosoft I updated the date_created and other time-related field all over the repo. Please review again.

[taprosoft]

Still missing date_created for uploaded file

kotaemon/libs/ktem/ktem/index/file/index.py

Line 75 in 908452c

"date_created": Column(

[cin-cris]

@taprosoft done changing all date_created field. Please kindly review.

[taprosoft]

LGTM

[taprosoft]

@cin-cris Thanks for your contribution.