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/admin.py

@@ -0,0 +1,72 @@
+from fastapi import APIRouter, Depends, HTTPException, Query
+from sqlalchemy.ext.asyncio import AsyncSession
+from typing import Annotated
+from app.database import get_db
+from app.services.admin import AdminService
+from app.api.v1.deps import get_current_user
+
+router = APIRouter()
+
+
+async def require_admin(current_user: dict = Depends(get_current_user)) -> dict:
+    if current_user.get("role") != "admin":
+        raise HTTPException(status_code=403, detail="Admin access required")
+    return current_user
+
+
+@router.get("/dashboard")
+async def get_dashboard(
+    _: dict = Depends(require_admin),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    service = AdminService(db)
+    return await service.get_dashboard()
+
+
+@router.get("/users")
+async def list_users(
+    page: int = Query(1, ge=1),
+    size: int = Query(20, ge=1, le=100),
+    _: dict = Depends(require_admin),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    service = AdminService(db)
+    return await service.list_users(page, size)
+
+
+@router.patch("/users/{target_user_id}/tier")
+async def update_user_tier(
+    target_user_id: str,
+    data: dict,
+    _: dict = Depends(require_admin),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    service = AdminService(db)
+    tier = data.get("tier")
+    if tier not in ("free", "pro", "enterprise"):
+        raise HTTPException(status_code=400, detail="Invalid tier")
+    success = await service.update_user_tier(target_user_id, tier)
+    if not success:
+        raise HTTPException(status_code=404, detail="User not found")
+    return {"message": f"User tier updated to {tier}"}
+
+
+@router.post("/users/{target_user_id}/toggle-active")
+async def toggle_user_active(
+    target_user_id: str,
+    _: dict = Depends(require_admin),
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    service = AdminService(db)
+    success = await service.toggle_user_active(target_user_id)
+    if not success:
+        raise HTTPException(status_code=404, detail="User not found")
+    return {"message": "User active status toggled"}
+
+
+@router.get("/health")
+async def system_health(
+    db: Annotated[AsyncSession, Depends(get_db)] = None,
+):
+    service = AdminService(db)
+    return await service.get_system_health()