The old test hit /api/games/lookup which is a public endpoint with no auth,
so it never checked the key — any key (or a deleted one) reported as valid.
- Add GET /api/plugin/verify-key endpoint that uses authenticateWithApiKey
to properly verify the x-api-key header via Better Auth
- Plugin test_api_key now calls /api/plugin/verify-key instead of games-lookup
- Returns the linked user's name + avatar on success for richer feedback