13538a4f41
Implements OAuth token management functions for Task 3: - save_token: persists access/refresh tokens with hashing - get_token_by_access/refresh: retrieves tokens by their hashes - increment_usage: tracks token usage count and last_used_at - revoke_token: sets revoked_at timestamp All 3 tests passing. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>