Use UTC timezone on timestamp/datetime columns

[stefanorosanelli]

This PR makes all timestamp/datetime columns timezone-aware (UTC) across the codebase and adds a new db_revision CLI command with associated tests.

• Convert existing model columns (created, modified, expires, locked_until, etc.) to use timezone=True and add descriptive comments
• Generate an Alembic migration to alter column types and add a unique constraint on config_key; update Alembic environment to include all models
• Introduce db_revision_cmd, register it in pyproject.toml, and add tests to verify its behavior

[Copilot]

Pull Request Overview

This PR makes all timestamp/datetime columns timezone-aware (UTC) across the codebase and adds a new db_revision CLI command with associated tests.

• Convert existing model columns (created, modified, expires, locked_until, etc.) to use timezone=True and add descriptive comments
• Generate an Alembic migration to alter column types and add a unique constraint on config_key; update Alembic environment to include all models
• Introduce db_revision_cmd, register it in pyproject.toml, and add tests to verify its behavior

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_commands.py	Add tests for the new db_revision_cmd
pyproject.toml	Register db_revision entry point
brevia/settings.py	Use TIMESTAMP(timezone=True) and add UniqueConstraint in ConfigStore
brevia/commands.py	Implement db_revision_cmd using Click
brevia/chat_history.py	Change DateTime to timezone-aware and add comments
brevia/async_jobs.py	Update timestamp handling to UTC and add comments
brevia/alembic/versions/eb659f4dd1c9_utc_timestamp.py	Auto-generated migration for timezone changes and unique constraint
brevia/alembic/env.py	Include all models in target_metadata for autogenerate
brevia/alembic/init.py	Expose a revision() helper for creating revisions

Comments suppressed due to low confidence (1)

brevia/commands.py:54

• [nitpick] For consistency with Click's output capture, use click.echo(f"New revision created: {message}") instead of print.

    print(f"New revision created: {message}")