feat(admin): app_config 运营配置后台(rewards 等常量可后台配置)

- 新增 app_config 表 + model/repository/config_schema + admin config 路由与 schema + 测试
- rewards.py 及 ad_reward/signin/task/wallet/comparison_milestone repositories 接入可配置项;ad.py / admin/main.py 配套
- alembic merge(ebb6af5c0b56)合并本地 app_config(cfg1a2b3c4d5)与 incoming price_report/best_deeplink(b7e2c1a9f4d3)两 head

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/models/__init__.py

@@ -2,6 +2,7 @@
 from app.models.ad_ecpm import AdEcpmRecord  # noqa: F401
 from app.models.ad_reward import AdRewardRecord  # noqa: F401
 from app.models.admin import AdminAuditLog, AdminUser  # noqa: F401
+from app.models.app_config import AppConfig  # noqa: F401
 from app.models.comparison import ComparisonRecord  # noqa: F401
 from app.models.comparison_milestone import ComparisonMilestoneClaim  # noqa: F401
 from app.models.feedback import Feedback  # noqa: F401

app/models/app_config.py

@@ -0,0 +1,32 @@
+"""运营可配置项(把 rewards.py 等硬编码规则挪到 DB,运营后台可改)。
+
+key 是配置标识(见 app.core.config_schema.CONFIG_DEFS),value 用 JSON 存任意值(int/list/dict)。
+表里没有的 key,业务读配置时 fallback 到 CONFIG_DEFS 默认值(= 原 rewards 常量),
+所以**空表 = 现有行为完全不变**。admin 改某项 → 写一行 → 业务下次读到新值(跨进程一致)。
+"""
+from __future__ import annotations
+
+from datetime import datetime
+from typing import Any
+
+from sqlalchemy import JSON, DateTime, Integer, String, func
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.db.base import Base
+
+_JSON = JSON().with_variant(JSONB(), "postgresql")
+
+
+class AppConfig(Base):
+    __tablename__ = "app_config"
+
+    key: Mapped[str] = mapped_column(String(64), primary_key=True)
+    value: Mapped[Any] = mapped_column(_JSON, nullable=False)
+    updated_by_admin_id: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
+    )
+
+    def __repr__(self) -> str:  # pragma: no cover
+        return f"<AppConfig key={self.key}>"