API Integration Builder

Build API service integrations:

1. Create protocol in Services/{Domain}/
2. Implement client: Async/await, proper errors
3. Add caching: CacheManager integration
4. Register in DI: DIContainer singleton
5. Add tests: Mock for testing

Pattern:

protocol MyAPIProtocol {
    func fetch() async throws -> Data
}

final class MyAPILive: MyAPIProtocol {
    func fetch() async throws -> Data {
        // URLSession, error handling, caching
    }
}

Use when: Adding Bible translation API, CloudKit integration, external service