MAINT Migrate internal callers of deprecated ScenarioResult.to_dict()/from_dict() to Pydantic API

[immu4989]

Fixes #2004.

ScenarioResult.to_dict() and ScenarioResult.from_dict(...) are marked for removal in 0.16.0. Internal PyRIT code still calls the deprecated forms, which emits a DeprecationWarning on every GET /api/scenarios/runs/{id}/results REST call and every CLI scenario result print.

Migration

The deprecated methods are thin wrappers around the Pydantic API. ScenarioResult.to_dict() delegates to self.model_dump(mode="json", by_alias=True) and ScenarioResult.from_dict(data) delegates to cls.model_validate(data). Output shape is identical, so the change is behavior-preserving.

Changes

• pyrit/backend/routes/scenarios.py: REST route now returns result.model_dump(mode="json", by_alias=True) and the response annotation is tightened from dict to dict[str, Any].
• pyrit/cli/_output.py: print_scenario_result_async deserializes with ScenarioResult.model_validate(result_dict).
• pyrit/cli/api_client.py: docstring on the matching CLI client method describes the new payload spelling.
• tests/unit/backend/test_scenario_run_routes.py: route test mocks model_dump instead of to_dict.
• tests/unit/cli/test_output.py: one test mocks model_validate instead of from_dict; the roundtrip integration test uses model_dump(mode="json", by_alias=True) to produce the payload.

Verification

# Targeted tests on the changed surface:
pytest tests/unit/backend tests/unit/cli
=> 906 passed in 8.18s

# Full unit suite, no regressions:
pytest tests/unit -n auto
=> 9794 passed, 5 skipped in 42.17s

# Pre-commit (ruff format, ruff check, ty type check, etc.):
pre-commit run
=> all hooks Passed