feat: 福利钱包+签到+省钱战绩+激励广告发奖+微信提现 后端

- 福利钱包: 金币/现金余额、流水、兑换 (api/v1/wallet.py, crud/wallet.py, models/wallet.py, schemas/welfare.py)
- 每日签到: 连续天数 + 档位奖励 (api/v1/signin.py, crud/signin.py, models/signin.py)
- 任务系统: "打开消息提醒"等任务领奖 (api/v1/tasks.py, crud/task.py, models/task.py)
- 省钱战绩: 省钱汇总/战绩/店铺菜品 (api/v1/savings.py, crud/savings.py, models/savings.py)
- 激励广告发奖: 穿山甲服务端回调 + 发奖规则 + 限流 (api/v1/ad.py, core/pangle.py, core/rewards.py, core/ratelimit.py, crud/ad_reward.py, schemas/ad.py, docs/ad_reward_golive_checklist.md)
- 微信提现: 商家转账到零钱 V3 (core/wxpay.py); user 表加微信 openid/nickname/avatar
- DB 迁移: 8 个 alembic (welfare 表/cash_transaction/openid 唯一约束/savings 店铺菜品/savings_record/ad_reward/withdraw_order+openid/user 微信字段)
- 运维脚本: reconcile_withdraws(对账) + reset_signin/reset_welfare + sim_pangle_callback(模拟穿山甲回调)
- 测试: test_welfare / test_withdraw / test_ad_reward
- 配置: .env.example + config.py 新增福利/广告/微信支付项; main.py 挂 5 个新路由

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/api/v1/tasks.py

@@ -0,0 +1,47 @@
+"""一次性任务 endpoint。
+
+路由前缀 `/api/v1/tasks`:
+  GET  /                    任务及领取状态(如"打开消息提醒")
+  POST /{task_key}/claim    领取任务奖励
+"""
+from __future__ import annotations
+
+import logging
+
+from fastapi import APIRouter, HTTPException, status
+
+from app.api.deps import CurrentUser, DbSession
+from app.crud import task as crud_task
+from app.schemas.welfare import TaskClaimResultOut, TaskListOut, TaskOut
+
+logger = logging.getLogger("shagua.tasks")
+
+router = APIRouter(prefix="/api/v1/tasks", tags=["tasks"])
+
+
+@router.get("", response_model=TaskListOut, summary="任务及领取状态")
+def list_tasks(user: CurrentUser, db: DbSession) -> TaskListOut:
+    states = crud_task.list_tasks(db, user.id)
+    return TaskListOut(
+        items=[
+            TaskOut(task_key=s.task_key, coin=s.coin, claimed=s.claimed)
+            for s in states
+        ]
+    )
+
+
+@router.post(
+    "/{task_key}/claim",
+    response_model=TaskClaimResultOut,
+    summary="领取任务奖励",
+)
+def claim_task(task_key: str, user: CurrentUser, db: DbSession) -> TaskClaimResultOut:
+    try:
+        coin, balance = crud_task.claim_task(db, user.id, task_key)
+    except crud_task.UnknownTaskError as e:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="unknown task") from e
+    except crud_task.AlreadyClaimedError as e:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="task already claimed") from e
+
+    logger.info("task claimed user_id=%d key=%s coin=%d", user.id, task_key, coin)
+    return TaskClaimResultOut(task_key=task_key, coin_awarded=coin, coin_balance=balance)