POST /api/v1/activate {"card":"XXXX-XXXX-XXXX-XXXX","hwid":"...","build":"<构建标记>","ts":}
→ {"ok":true,"token":"...","kmat":"<32字节hex>","expire_at":0,
"policy":{"grace_hours":12,"expire_at":0,"sig":""}}
POST /api/v1/heartbeat {"token":"...","hwid":"..."}
→ {"ok":true,"kmat":"...","expire_at":...,"server_time":...,"policy":{...}}
POST /api/v1/deactivate {"token":"...","hwid":"..."}
GET /api/v1/ping | /api/v1/time