feat(adapters): 接入 CloudCone/Zeabur/Dynadot/新网/Agnes 五个平台

线上平台列表里 cloudcone、zeabur、xinwang、dynadot、agnes 的 sdk_type 仍为空，
平台卡片只能显示「未对接」，用户无法同步。按各自真实 API 能力补齐：

- CloudCone：实例清单 + 开机/关机/重启；无公开账单接口，不声明余额与续费
- Zeabur：服务器清单 + 重启；毫核/MB 归一化为核/GB，未采集时不伪造规格
- Dynadot：域名清单（含到期日）+ 账户余额；set_dns2 位置参数无法安全 CRUD
- 新网：代理 API 按域名逐个查到期日；无列表接口，需在账号里填 domains 清单
- Agnes：/models 校验 Key；无余额接口，如实标记不支持

配套改动：
- _align_preset_providers 为库中为空的 sdk_type 回填种子值（启动即生效），
  避免新适配器上线后线上仍停留在「未对接」
- 适配器可声明 plain_config，代理号/域名等非密钥字段前端按明文输入
- PRESET_PROVIDERS 五条记录填上对应 sdk_type

测试：445 passed（新增 tests/test_platform_adapters.py），vitest 62 passed。

app/core/seed.py

@@ -39,25 +39,24 @@ PRESET_PROVIDERS = [
     {"slug": "tothost", "name": "TotHost", "name_en": "TotHost", "category": "vps",
      "services": "vps",
      "website": "https://www.tothost.vn", "console_url": "https://billing.tothost.vn/clientarea.php", "sdk_type": "whmcs-panel"},
-    # 以下平台暂无适配器：sdk_type 必须留空。
-    # 填了不存在的 sdk_type 会让平台卡片显示「API 对接: xxx」，用户建账号点同步才撞
-    # 「暂不支持的 SDK 类型」——声明支持却不支持，比明说不支持更糟。
     {"slug": "cloudcone", "name": "CloudCone", "name_en": "CloudCone", "category": "vps",
      "services": "vps",
-     "website": "https://cloudcone.com", "console_url": "https://app.cloudcone.com", "sdk_type": None},
+     "website": "https://cloudcone.com", "console_url": "https://app.cloudcone.com", "sdk_type": "cloudcone-api"},
     {"slug": "zeabur", "name": "Zeabur", "name_en": "Zeabur", "category": "vps",
      "services": "vps,domain",
-     "website": "https://zeabur.com", "console_url": "https://dash.zeabur.com", "sdk_type": None},
+     "website": "https://zeabur.com", "console_url": "https://dash.zeabur.com", "sdk_type": "zeabur-api"},
     # ---- 域名注册商 ----
     {"slug": "namesilo", "name": "Namesilo", "name_en": "Namesilo", "category": "domain",
      "services": "domain,dns",
      "website": "https://namesilo.com", "console_url": "https://www.namesilo.com/account_domains.php", "sdk_type": "namesilo-api"},
+    # 新网只有代理账号能调 API，且没有「列出全部域名」的接口：需在账号里
+    # 填写 domains 清单；零售客户区有验证码，无法用面板抓取替代。
     {"slug": "xinwang", "name": "新网", "name_en": "Xinnet", "category": "domain",
      "services": "domain,dns",
-     "website": "https://xinnet.com", "console_url": "https://www.xinnet.com", "sdk_type": None},
+     "website": "https://xinnet.com", "console_url": "https://www.xinnet.com", "sdk_type": "xinnet-api"},
     {"slug": "dynadot", "name": "Dynadot", "name_en": "Dynadot", "category": "domain",
      "services": "domain,dns",
-     "website": "https://dynadot.com", "console_url": "https://www.dynadot.com/account/domains", "sdk_type": None},
+     "website": "https://dynadot.com", "console_url": "https://www.dynadot.com/account/domains", "sdk_type": "dynadot-api"},
     # ---- AI 服务商 ----
     {"slug": "openai", "name": "OpenAI", "name_en": "OpenAI", "category": "ai_agent",
      "services": "ai_agent",
@@ -70,7 +69,7 @@ PRESET_PROVIDERS = [
      "website": "https://moonshot.cn", "console_url": "https://platform.moonshot.cn", "sdk_type": "moonshot-api"},
     {"slug": "agnes", "name": "Agnes", "name_en": "Agnes", "category": "ai_agent",
      "services": "ai_agent",
-     "website": None, "console_url": None, "sdk_type": None},
+     "website": None, "console_url": None, "sdk_type": "agnes-api"},
     {"slug": "deepseek", "name": "DeepSeek", "name_en": "DeepSeek", "category": "ai_agent",
      "services": "ai_agent",
      "website": "https://deepseek.com", "console_url": "https://platform.deepseek.com", "sdk_type": "deepseek-api"},