docs(admin): 补充管理后台 API 与数据库文档 (#12)

新增 admin 模块接口文档(auth login/me、admins CRUD、audit-logs、feedback 处理、stats 概览、user coins/detail/status、wallet 流水、withdraw 对账/刷新/列表) + admin_user/admin_audit_log 两张表文档，更新 api/database README 索引。

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

---------

Co-authored-by: OuYingJun1024 <1034284404@qq.com>
Reviewed-on: #12
Co-authored-by: ouzhou <ouzhou@wonderable.ai>
Co-committed-by: ouzhou <ouzhou@wonderable.ai>

app/schemas/compare_record.py

@@ -37,6 +37,9 @@ class ComparisonResultIn(BaseModel):
     # 必须显式声明: 落库走 model_dump(), pydantic 默认丢未知字段, 不声明这行会被悄悄吞掉。
     # 各平台抠到红包即带值(2026-06 起源平台 Phase1 意图识别也抠, 当前仅淘宝源)。见 pricebot 侧 比价红包额留痕-实现方案.md。
     coupon_saved: float | None = None
+    # 优惠**来源名**(展示用, best-effort): 美团"外卖大额神券"/京东"百亿补贴"/淘宝"平台红包"。
+    # None=没抠到 → 前端走通用"红包"。同样必须显式声明否则上报边界被 pydantic 静默丢弃(pricebot#38 引入)。
+    coupon_name: str | None = None
 
 
 class ComparisonRecordIn(BaseModel):

app/schemas/welfare.py

@@ -199,6 +199,7 @@ class SavingsBattleOut(BaseModel):
     week_saved_cents: int = Field(..., description="本周已省(分)")
     beat_percent: int = Field(..., description="超过百分之多少用户")
     streak_days: int = Field(..., description="连续省钱天数")
+    compare_count: int = Field(..., description="累计完成比价次数(= 比价上报记录数)")
 
 
 class SavingsRecordOut(BaseModel):