fix: quote SMS.Provider off to avoid YAML bool parse

Bare off is boolean in YAML 1.1 and crashed platform on startup with type mismatch.

Co-authored-by: Cursor <cursoragent@cursor.com>

platform/etc/platform.yaml

@@ -19,11 +19,12 @@ Auth:
   RequirePhoneBound: false
 
 SMS:
-  Provider: off
+  # 须加引号：YAML 1.1 会把裸 off/on 当成布尔，导致 type mismatch for field sms.provider
+  Provider: "off"
   CodeTTLSeconds: 300   # 短信验证码有效期（秒）
   ResendSeconds: 60
   # DevFixedCode: "123456"
-  # 试运行未接短信平台：false；正式接入后改为 true，且 Provider 勿用 off
+  # 试运行未接短信平台：false；正式接入后改为 true，且 Provider 勿用 "off"
   RequireForBind: false
 
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