feat: 管理看板全面改版 — 增强可读性 + 填充空白区域

后端增强:
  - DashboardStats 新增 tasks_rejected, tasks_rework, unread_notifications
  - 新增 GET /dashboard/recent-activity 最近动态端点
  - 关联 Task + Product 表返回完整动态信息

前端改版 (AdminDashboard.tsx):
  - 4 张概览卡片: 产品流转 | 任务状态 | 品质通知 | 完成率
  - 每张卡片含进度条(百分比标注) + 中文说明
  - SVG 环形图展示任务完成率
  - 最近流转动态时间线 (8条)
  - 快捷入口: 创建产品/任务管理/打印配置/扫码干活
  - 底部说明卡片解释"产品 vs 任务"的区别
  - 响应式网格填满全屏, 无空白区域

backend/app/services/dashboard_service.py

@@ -5,19 +5,38 @@ from pydantic import BaseModel
 
 
 class DashboardStats(BaseModel):
+    # 产品
     products_total: int
     products_pending: int
     products_in_progress: int
     products_completed: int
+    # 任务
     tasks_total: int
     tasks_pending: int
     tasks_in_progress: int
     tasks_completed: int
+    tasks_rejected: int
+    tasks_rework: int
+    # 通知
+    unread_notifications: int = 0
+
+
+class RecentActivity(BaseModel):
+    action: str
+    task_name: str
+    operator: str
+    product_sn: str
+    time: str
+    remark: str | None = None
 
 
 async def get_dashboard_stats(db: AsyncSession) -> DashboardStats:
     from app.models.product import Product
-    from app.models.task import Task, TASK_STATUS_PENDING, TASK_STATUS_WIP, TASK_STATUS_COMPLETED
+    from app.models.task import (
+        Task, TASK_STATUS_PENDING, TASK_STATUS_WIP, TASK_STATUS_COMPLETED,
+        TASK_STATUS_REJECTED, TASK_STATUS_ARCHIVED,
+    )
+    from app.models.notification import Notification
 
     p_total = await db.scalar(select(func.count(Product.id)))
     p_pending = await db.scalar(select(func.count(Product.id)).where(Product.status == "pending"))
@@ -28,6 +47,12 @@ async def get_dashboard_stats(db: AsyncSession) -> DashboardStats:
     t_pending = await db.scalar(select(func.count(Task.id)).where(Task.status == TASK_STATUS_PENDING))
     t_progress = await db.scalar(select(func.count(Task.id)).where(Task.status == TASK_STATUS_WIP))
     t_done = await db.scalar(select(func.count(Task.id)).where(Task.status == TASK_STATUS_COMPLETED))
+    t_rejected = await db.scalar(select(func.count(Task.id)).where(Task.status == TASK_STATUS_REJECTED))
+    t_rework = await db.scalar(select(func.count(Task.id)).where(Task.is_rework.is_(True)))
+
+    unread = await db.scalar(
+        select(func.count(Notification.id)).where(Notification.is_read.is_(False))
+    )
 
     return DashboardStats(
         products_total=p_total or 0,
@@ -38,4 +63,50 @@ async def get_dashboard_stats(db: AsyncSession) -> DashboardStats:
         tasks_pending=t_pending or 0,
         tasks_in_progress=t_progress or 0,
         tasks_completed=t_done or 0,
+        tasks_rejected=t_rejected or 0,
+        tasks_rework=t_rework or 0,
+        unread_notifications=unread or 0,
     )
+
+
+async def get_recent_activity(db: AsyncSession, limit: int = 10) -> list[RecentActivity]:
+    from app.models.task_log import TaskLog
+    from app.models.task import Task
+    from app.models.product import Product
+
+    stmt = (
+        select(TaskLog, Task.task_name, Product.serial_number)
+        .join(Task, TaskLog.task_id == Task.id)
+        .join(Product, Task.product_id == Product.id)
+        .order_by(TaskLog.created_at.desc())
+        .limit(limit)
+    )
+    result = await db.execute(stmt)
+    rows = result.all()
+
+    activities: list[RecentActivity] = []
+    for log, task_name, product_sn in rows:
+        action_label = _action_label(log.action_type)
+        time_str = log.created_at.strftime("%m-%d %H:%M") if log.created_at else ""
+        activities.append(RecentActivity(
+            action=action_label,
+            task_name=task_name or "",
+            operator=log.operator_id or "系统",
+            product_sn=product_sn or "",
+            time=time_str,
+            remark=log.remark,
+        ))
+    return activities
+
+
+def _action_label(action_type: str) -> str:
+    labels = {
+        "create": "创建任务",
+        "receive": "确认接收",
+        "complete": "完成任务",
+        "transfer": "完工转交",
+        "reject": "品质驳回",
+        "end": "结束分支",
+        "recall": "撤回转交",
+    }
+    return labels.get(action_type, action_type)