chore(alembic): 合并 pages_override 与领券成功率两个迁移 head,修复 upgrade head(单数)多 head 报错

pull main 带入 #126 的 admin_user_pages_override,与本分支领券成功率的
coupon_session_platform_success → coupon_claim_app_env 都从 admin_user_plain_password
分叉,形成两个 alembic head。多 head 会让部署/run.sh 用的 `alembic upgrade head`(单数)
报 "Multiple head revisions are present" 而中断。

本迁移为纯 merge:upgrade/downgrade 均空,不含任何表结构或数据改动,仅把两个 head
收敛为单 head(merge_pages_override_coupon_slot),使 `alembic upgrade head` 恢复正常。

app/api/v1/auth.py

@@ -12,12 +12,17 @@ from __future__ import annotations
 
 import logging
 
-from fastapi import APIRouter, HTTPException, Request, status
+from fastapi import APIRouter, HTTPException, Request
 from sqlalchemy.exc import IntegrityError
 
 from app.api.deps import CurrentUser, DbSession
 from app.core import test_account
-from app.core.ratelimit import enforce_rate_limit
+from app.core.ratelimit import (
+    RateLimitRule,
+    check_rate_limits,
+    enforce_rate_limit,
+    record_rate_limits,
+)
 from app.core.security import (
     TokenError,
     create_bind_ticket,
@@ -28,13 +33,6 @@ from app.core.security import (
     issue_token_pair,
 )
 from app.integrations import wxpay
-from app.core.ratelimit import (
-    RateLimitRule,
-    check_rate_limits,
-    enforce_rate_limit,
-    record_rate_limits,
-)
-from app.core.security import TokenError, decode_token, issue_token_pair
 from app.integrations.jiguang import JiguangError, mask_phone, verify_and_get_phone
 from app.integrations.sms import SmsError, send_code, verify_code
 from app.repositories import onboarding as onboarding_repo