SI-3: Migrate auth_key context to contract-first architecture

[josecelano]

Subissue of EPIC #1938 — REST API Contract-First Migration

Problem

The auth_key context has 4 handlers and 7 response functions defined locally in axum-rest-api-server. It calls tracker_core::authentication::{Key, AddKeyRequest, KeysHandler} directly. Local DTOs (AuthKey, AddKeyForm, KeyParam) should live in rest-api-protocol.

Scope

• Move AuthKey, AddKeyForm, KeyParam DTOs to rest-api-protocol/src/v1/resources/auth_key.rs
• Define AuthKeyCommandPort trait in rest-api-application/src/ports/
• Implement AuthKeyApiService use-case
• Implement TrackerAuthKeyAdapter in rest-api-runtime-adapter wrapping KeysHandler + clock
• Rewire Axum handlers to use AuthKeyApiService

Checklist

• Protocol DTOs created and exported
• AuthKeyCommandPort trait defined
• AuthKeyApiService use-case implemented
• TrackerAuthKeyAdapter implemented
• Axum handlers dispatch through use-case
• Pre-commit checks pass
• Pre-push checks pass