fix(sms): auth sms_send 接入 SendResult(修 cooldown_sec 500)+ 记 provider/fallback

批次2 将 send_code 返回类型 int→SendResult 后,sms_send 仍把它整体塞进
SmsSendResponse.cooldown_sec:int → pydantic ValidationError → 500。改为取
send_result.cooldown_sec;成功侧 EVENT_SMS_SEND details 加 provider/fallback。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/api/v1/auth.py

@@ -207,7 +207,8 @@ def sms_send(req: SmsSendRequest, request: Request, db: DbSession) -> SmsSendRes
     check_rate_limits(request, subject=req.device_id, rules=send_rules)
 
     try:
-        cooldown = send_code(req.phone)
+        send_result = send_code(req.phone)
+        cooldown = send_result.cooldown_sec
     except SmsError as e:
         risk_repo.record_behavior_event(
             db,
@@ -238,7 +239,9 @@ def sms_send(req: SmsSendRequest, request: Request, db: DbSession) -> SmsSendRes
         phone=req.phone,
         client_ip=_client_ip(request),
         outcome="success",
-        details={"mock": settings.SMS_MOCK},
+        details={"mock": settings.SMS_MOCK,
+                 "provider": send_result.provider,
+                 "fallback": send_result.fallback},
         evaluate_rule=risk_repo.RULE_SMS_HOURLY,
     )