FEAT: Supporting Converter Configuration on REST API

[Richard Lundeen (rlundeen2)]

Description

Adds REST support for ordered, registry-backed request and response converter configurations without changing the PromptNormalizer contract.

• Preserves converter order, piece-index selectors, and prompt data-type selectors.
• Resolves registry IDs once before message persistence and reuses the resolved configurations for converter tracking.
• Keeps the legacy global converter_ids request pipeline for compatibility and emits a deprecation warning for removal in PyRIT 1.3.0.
• Rejects conflicting legacy and structured request fields, invalid selectors, and converter configurations when send=False.
• Excludes only client-preconverted pieces from request conversion while retaining conversion for other eligible pieces.

Tests and Documentation

• Added backend service and route coverage for ordering, targeting, response forwarding, legacy compatibility and warnings, validation, missing registry IDs, metadata tracking, and preconverted pieces.
• Ran UV_NO_SYNC=1 uv run --no-sync python -m pytest tests/unit/backend/test_attack_service.py tests/unit/backend/test_api_routes.py -q (206 passed).
• Ran UV_NO_SYNC=1 uv run --no-sync pre-commit run --all-files (all hooks passed).
• Updated REST model and route descriptions. JupyText is not applicable.