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/api/v1/ad.py

@@ -71,7 +71,7 @@ def pangle_callback(request: Request, db: DbSession) -> PangleCallbackOut:
         return PangleCallbackOut(is_verify=False, reason=REASON_BAD_PARAMS)
 
     user_id = int(raw_user_id)
-    coin = rewards.resolve_ad_reward_coin(params.get("reward_amount"))
+    coin = rewards.resolve_ad_reward_coin(db, params.get("reward_amount"))
     raw = "&".join(f"{k}={v}" for k, v in sorted(params.items()) if k != "sign")
     try:
         rec = crud_ad.grant_ad_reward(