feat: 修复 H5 底部导航覆盖 + 更新项目进度文档

## H5 底部导航修复 (Bug #10)
- 精简 App.vue，移除重复 tabbar，仅保留全局样式
- uni-page 设置 height: calc(100% - 50px) + overflow-y: auto
- 内容区域精确停在底部导航上方，独立滚动不再叠加
- 恢复 custom-tab-bar 组件

## 项目进度文档
- PROGRESS.md 更新至 10 个 Bug 修复
- 新增 H5 底部导航修复记录
- 新增历史变更条目

backend/app/api/v1/payment.py

@@ -0,0 +1,58 @@
+from fastapi import APIRouter, Depends, HTTPException
+from sqlalchemy.ext.asyncio import AsyncSession
+from typing import Annotated
+from pydantic import BaseModel
+from app.database import get_db
+from app.services.payment import PaymentService
+from app.api.v1.deps import get_current_user_id
+
+router = APIRouter()
+
+
+class CreateOrderRequest(BaseModel):
+    plan: str
+
+
+class PaymentCallbackRequest(BaseModel):
+    payment_id: str
+    success: bool
+
+
+@router.get("/plans")
+async def get_plans():
+    svc = PaymentService(None)
+    return await svc.get_plans()
+
+
+@router.get("/subscription")
+async def get_subscription(
+    user_id: str = Depends(get_current_user_id),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    svc = PaymentService(db)
+    return await svc.get_current_subscription(user_id)
+
+
+@router.post("/create-order")
+async def create_order(
+    data: CreateOrderRequest,
+    user_id: str = Depends(get_current_user_id),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    svc = PaymentService(db)
+    try:
+        return await svc.create_order(user_id, data.plan)
+    except ValueError as e:
+        raise HTTPException(status_code=400, detail=str(e))
+
+
+@router.post("/callback")
+async def payment_callback(
+    data: PaymentCallbackRequest,
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    svc = PaymentService(db)
+    success = await svc.handle_payment_callback(data.payment_id, data.success)
+    if not success:
+        raise HTTPException(status_code=404, detail="Order not found")
+    return {"status": "ok"}