Evaluate Pydantic Settings for runtime configuration parsing

[mark-e-deyoung]

Summary

Evaluate replacing WineBot's custom environment/config parsing with Pydantic Settings or an equivalent widely used configuration library.

Candidate scope

• api/utils/config.py
• api/core/config_guard.py
• profile/config validation helpers and tests
• generated or documented config metadata for winebotctl config describe

Acceptance criteria

• Runtime configuration has typed settings, defaults, validation, and clear error messages.
• Environment variable names and backward compatibility are preserved.
• Required dependency is added to runtime requirements and image build paths.
• Existing strict config tests pass and new tests cover invalid values and compatibility aliases.
• If Pydantic Settings is rejected, document why the custom implementation remains preferable.

Recommendation

Defer until after the current release gate unless config metadata is release-critical. Implement in a separate PR because config parsing affects boot behavior.

Trade-offs

Pydantic Settings reduces custom validation code and improves maintainability, but it adds a runtime dependency and can change parsing semantics if migrated carelessly.