* Wire Redis infrastructure into auth-server

Add Redis configuration, lifecycle management, and DI plumbing for auth-server so future OAuth state storage can use the shared Redis client.

* Add Redis-backed OAuth state store

Introduce OAuthStateStore for Redis-backed clients, auth codes, refresh tokens, and device flow state with hashed client secrets, atomic token consumption, and focused unit coverage.

* Migrate auth OAuth routes to Redis state store

Replace in-memory OAuth state usage with OAuthStateStore, add DCR client validation for auth/token flows, and update route tests around Redis-backed state semantics.

* Align OAuth route tests with state store contract

Introduce an in-memory OAuth state store test double that follows the production store protocol, allowing route tests to validate Redis migration behavior without requiring a live Redis instance.

* fix: findings M1 m2 m3 m4 m5

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Co-authored-by: kxue43 <kent.xue@ascendingdc.com>