Add OpenAPI/Swagger contract tests and handle nested id UUIDs

[merval]

Motivation

• Ensure the application’s HTTP requests to ProPresenter remain aligned with the checked-in OpenAPI/Swagger spec to catch API contract regressions early.
• Correctly extract stable UUID-like identifiers when the API returns nested id objects to avoid broken library/presentation lookups.

Description

• Add tests/openapi_spec.py helpers to load the checked-in tests/swagger.json, match concrete API paths to templated OpenAPI paths, and extract example JSON responses.
• Add tests/test_swagger_contract.py which injects a FakeProPresenterClient, exercises the app routes, and asserts each generated ProPresenter request is covered by the OpenAPI spec and example fixtures.
• Update propresenter_notes/services.py uuid_value to recurse into a nested id dict when present so nested `{

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Codex Task