fix: 3个逻辑/UI Bug修复

Bug1 — 任务总数与进度条不匹配:
  tasks_total 从全库历史总数改为 PENDING+WIP+COMPLETED(时段)+REJECTED(时段)
  确保进度条4段之和 = 显示的总数, 不再出现11≠9的缺口

Bug2 — 在制品排序混乱:
  移除DB层order_by, 改为Python统一按duration_hours降序
  无视status, 纯数值排序, 滞留最久排最前
  取limit*2条后在Python中排序再截断

Bug3 — 留言板产品显示割裂:
  [Tag:SN] 物料名 → 物料名 (SN: A1B2C3D4...)
  物料名加粗, SN等宽灰色, 阅读更顺畅

backend/app/services/dashboard_service.py

@@ -78,8 +78,7 @@ async def get_dashboard_stats(
     p_progress = await db.scalar(select(func.count(Product.id)).where(Product.status == "in_progress"))
     p_done = await db.scalar(select(func.count(Product.id)).where(Product.status == "completed"))
 
-    # ── 任务总数 & 实时快照（PENDING/WIP/返工 — 永远不过滤） ──
-    t_total = await db.scalar(select(func.count(Task.id)))
+    # ── 任务实时快照（PENDING/WIP/返工 — 永远不过滤） ──
     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_rework = await db.scalar(select(func.count(Task.id)).where(Task.is_rework.is_(True)))
@@ -96,6 +95,9 @@ async def get_dashboard_stats(
     t_done = await db.scalar(t_done_q)
     t_rejected = await db.scalar(t_rej_q)
 
+    # ── 任务总数 = 实时快照段 + 时间过滤段（确保进度条段总和=总数） ──
+    t_total = (t_pending or 0) + (t_progress or 0) + (t_done or 0) + (t_rejected or 0)
+
     # ── 通知 & 留言（实时快照） ──
     unread_notif = await db.scalar(
         select(func.count(Notification.id)).where(Notification.is_read.is_(False))
@@ -131,8 +133,7 @@ async def get_wip_tasks(db: AsyncSession, limit: int = 20) -> list[WipTask]:
         select(Task, Product.serial_number)
         .join(Product, Task.product_id == Product.id)
         .where(Task.status.in_([TASK_STATUS_PENDING, TASK_STATUS_WIP]))
-        .order_by(Task.received_at.asc().nulls_last(), Task.created_at.asc())
-        .limit(limit)
+        .limit(limit * 2)  # 多取一些，后面 Python 统一排序
     )
     result = await db.execute(stmt)
     rows = result.all()
@@ -167,7 +168,9 @@ async def get_wip_tasks(db: AsyncSession, limit: int = 20) -> list[WipTask]:
             received_at=recv_str,
             duration_hours=hours,
         ))
-    return wip_list
+    # 统一按滞留时间降序排列（无视 status，纯数值排序）
+    wip_list.sort(key=lambda t: t.duration_hours, reverse=True)
+    return wip_list[:limit]
 
 
 # ============================================================

frontend/src/pages/admin/AdminDashboard.tsx

@@ -4,7 +4,7 @@ import {
   RefreshCw, Loader2, AlertCircle, ArrowRight, Clock, MessageCircle,
 } from "lucide-react";
 import { useNavigate } from "react-router-dom";
-import { Radio, DatePicker, Drawer, Input, Tag } from "antd";
+import { Radio, DatePicker, Drawer, Input } from "antd";
 import dayjs, { type Dayjs } from "dayjs";
 import {
   fetchDashboardStats, fetchWipTasks, fetchDashboardMessages,
@@ -127,11 +127,11 @@ function MsgRow({ m }: { m: ProductMessageItem }) {
             <span className="shrink-0 text-xs text-gray-400">{t}</span>
           </div>
           <p className="mb-2 text-sm leading-relaxed text-gray-600">{m.content}</p>
-          <div className="flex items-center gap-2">
-            <Tag color="blue" className="m-0 text-xs font-mono">{m.product_sn}</Tag>
+          <div className="flex items-center gap-1 text-xs text-gray-500">
             {m.material_name && (
-              <span className="truncate text-xs text-gray-500">{m.material_name}</span>
+              <span className="font-medium text-gray-700">{m.material_name}</span>
             )}
+            <span className="font-mono text-gray-400">(SN: {m.product_sn})</span>
           </div>
         </div>
       </div>