refactor: 重构 token 管理，新增 NATS adapter 和多示例

按照 TOKEN_REFACTOR.md / FIX_CONFIG.md 方案重构核心层：
- miot: Init() 优先读 storage token，新增 RefreshAuthInfo() 和刷新回调
- xiaomi: Config 改用 AuthInfo 结构体（含 UUID/UID/DataDir/OnTokenRefreshed）
- xiaomi: NewClient(ctx, Config) 新签名，新增 RefreshToken()，后台自动刷新
- xiaomi/devices: 设备控制接口重构
- 新增示例 12_ac_subscribe，其余示例适配新 Config

xiaomi/examples/12_ac_subscribe/data/cert/mihome_ca.cert

@@ -0,0 +1,21 @@
+-----BEGIN CERTIFICATE-----
+MIIBazCCAQ+gAwIBAgIEA/UKYDAMBggqhkjOPQQDAgUAMCIxEzARBgNVBAoTCk1p
+amlhIFJvb3QxCzAJBgNVBAYTAkNOMCAXDTE2MTEyMzAxMzk0NVoYDzIwNjYxMTEx
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+EwQFMAMBAf8wHQYDVR0OBBYEFJa3onw5sblmM6n40QmyAGDI5sURMAwGCCqGSM49
+BAMCBQADSAAwRQIgchciK9h6tZmfrP8Ka6KziQ4Lv3hKfrHtAZXMHPda4IYCIQCG
+az93ggFcbrG9u2wixjx1HKW4DUA5NXZG0wWQTpJTbQ==
+-----END CERTIFICATE-----
+-----BEGIN CERTIFICATE-----
+MIIBjzCCATWgAwIBAgIBATAKBggqhkjOPQQDAjAiMRMwEQYDVQQKEwpNaWppYSBS
+b290MQswCQYDVQQGEwJDTjAgFw0yMjA2MDkxNDE0MThaGA8yMDcyMDUyNzE0MTQx
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+CVpZPwgj9e9Ve5r3K7zvu8Jjj7JF1JjQYvEC6yhp1SzBgglnK4L8xQzdiqNQME4w
+HQYDVR0OBBYEFCf9+YBU7pXDs6K6CAQPRhlGJ+cuMB8GA1UdIwQYMBaAFJa3onw5
+sblmM6n40QmyAGDI5sURMAwGA1UdEwQFMAMBAf8wCgYIKoZIzj0EAwIDSAAwRQIh
+AKUv+c8v98vypkGMTzMwckGjjVqTef8xodsy6PhcSCq+AiA/n9mDs62hAo5zXyJy
+Bs1s7mqXPf1XgieoxIvs1MqyiA==
+-----END CERTIFICATE-----