fix: Return UTC-aware datetimes from unmarshalling

[abrookins]

Summary

Fixes #807 - Unmarshalled datetime fields are now UTC-aware instead of naive local time.

Problem

Previously, datetime fields were unmarshalled using datetime.fromtimestamp(value) which returns a naive datetime in the server's local timezone. This caused:

• Non-deterministic behavior depending on server timezone
• Inability to compare retrieved datetimes with timezone-aware datetimes
• Time jumps around daylight savings transitions

Solution

Changed unmarshalling to use datetime.fromtimestamp(value, datetime.timezone.utc) which returns a UTC-aware datetime. This follows the standard ORM pattern of storing UTC and returning UTC-aware datetimes.

Breaking Change

Retrieved datetime fields are now UTC-aware instead of naive local time. Code that compared retrieved datetimes with naive datetimes will need to either:

1. Make the comparison datetime UTC-aware, or
2. Use .timestamp() for comparison

Tests

Added new tests for timezone-aware datetime handling and updated existing tests to work with the new behavior.

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Co-authored by Augment Code

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Note

Medium Risk
Changes core datetime/date (de)serialization and query value normalization, which can break consumers expecting naive/local-time datetimes and may subtly affect date equality behavior across timezones.

Overview
Standardizes datetime handling to UTC. Timestamp unmarshalling now uses datetime.fromtimestamp(..., datetime.timezone.utc) so retrieved datetime values are timezone-aware, and date values are stored/query-normalized to UTC midnight to avoid timezone-dependent day shifts.

Updates numeric query value conversion to match the new UTC normalization and adjusts tests to assert UTC-aware behavior, adding explicit coverage for timezone-aware inputs and timezone-independent date round-trips/queries. Separately, the sync-code generator (make_sync.py) now post-fixes a duplicated redisvl import and runs ruff format on generated sync output to satisfy CI linting.

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