refactor(dashboard): V2 审计重构 — i18n 补齐 + 共享抽象 + 单测 + a11y

V2 审计报告（docs/architecture/audit/dashboard-audit-report-v2.md）发现并修复：

- P0 i18n：10 个子组件硬编码字符串全部接入 next-intl（teacher-quick-actions /
  teacher-classes-card / teacher-homework-card / teacher-schedule /
  recent-submissions / teacher-grade-trends / student-grades-card /
  student-today-schedule-card / student-upcoming-assignments-card /
  admin-dashboard），新增 ~50 个翻译键
- P1 共享抽象：新增 DashboardGreetingHeader 组件，消除 teacher/student
  头部 90% 重复代码，两个 Header 改为薄包装
- P2 单测：为 6 个纯函数添加 31 个单元测试
  （tests/integration/dashboard/dashboard-utils.test.ts）
- P2 a11y：admin 表格 caption、teacher/student 视图语义化标签
  （header / section aria-label / aside aria-label）
- 同步架构图 004/005

src/modules/dashboard/components/teacher-dashboard/teacher-schedule.tsx

@@ -1,150 +1,147 @@
-import Link from "next/link";
-import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card";
-import { Badge } from "@/shared/components/ui/badge";
-import { CalendarDays, CalendarX, MapPin } from "lucide-react";
-import { EmptyState } from "@/shared/components/ui/empty-state";
-import { cn } from "@/shared/lib/utils";
-import { ScrollArea } from "@/shared/components/ui/scroll-area";
+import Link from "next/link"
+import { getTranslations } from "next-intl/server"
+import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
+import { Badge } from "@/shared/components/ui/badge"
+import { CalendarDays, CalendarX, MapPin } from "lucide-react"
+import { EmptyState } from "@/shared/components/ui/empty-state"
+import { cn } from "@/shared/lib/utils"
+import { ScrollArea } from "@/shared/components/ui/scroll-area"
 
 type TeacherTodayScheduleItem = {
-  id: string;
-  classId: string;
-  className: string;
-  course: string;
-  startTime: string;
-  endTime: string;
-  location: string | null;
-};
+  id: string
+  classId: string
+  className: string
+  course: string
+  startTime: string
+  endTime: string
+  location: string | null
+}
+
+export async function TeacherSchedule({ items }: { items: TeacherTodayScheduleItem[] }) {
+  const t = await getTranslations("dashboard")
+  const hasSchedule = items.length > 0
 
-export function TeacherSchedule({ items }: { items: TeacherTodayScheduleItem[] }) {
-  const hasSchedule = items.length > 0;
-  
   const getStatus = (start: string, end: string) => {
-    const now = new Date();
-    const currentTime = now.getHours() * 60 + now.getMinutes();
-    
-    const [startH, startM] = start.split(":").map(Number);
-    const [endH, endM] = end.split(":").map(Number);
-    const startTime = startH * 60 + startM;
-    const endTime = endH * 60 + endM;
+    const now = new Date()
+    const currentTime = now.getHours() * 60 + now.getMinutes()
 
-    if (currentTime >= startTime && currentTime <= endTime) return "live";
-    if (currentTime < startTime) return "upcoming";
-    return "past";
-  };
+    const [startH, startM] = start.split(":").map(Number)
+    const [endH, endM] = end.split(":").map(Number)
+    const startTime = (startH ?? 0) * 60 + (startM ?? 0)
+    const endTime = (endH ?? 0) * 60 + (endM ?? 0)
+
+    if (currentTime >= startTime && currentTime <= endTime) return "live"
+    if (currentTime < startTime) return "upcoming"
+    return "past"
+  }
 
   return (
-      <Card>
+    <Card>
       <CardHeader className="pb-3">
         <CardTitle className="flex items-center gap-2 text-base">
           <CalendarDays className="h-4 w-4 text-muted-foreground" />
-          Today&apos;s Schedule
+          {t("sections.todaySchedule")}
         </CardTitle>
       </CardHeader>
       <CardContent className="p-0">
         {!hasSchedule ? (
-           <EmptyState
-             icon={CalendarX}
-             title="No Classes Today"
-             description="No timetable entries."
-             action={{ label: "View schedule", href: "/teacher/classes/schedule" }}
-             className="border-none h-[200px]"
-           />
+          <EmptyState
+            icon={CalendarX}
+            title={t("empty.noClassesToday")}
+            description={t("empty.noClassesTodayDesc")}
+            action={{ label: t("quickActions.viewSchedule"), href: "/teacher/classes/schedule" }}
+            className="border-none h-[200px]"
+          />
         ) : (
           <ScrollArea className="h-[240px] px-6 py-2">
             <div className="relative space-y-0 ml-1">
-               {/* Vertical Timeline Line */}
               <div className="absolute left-[11px] -top-2 -bottom-2 w-px bg-border/50" />
-              
-              {/* Top Fade Hint */}
+
               <div className="absolute left-[11px] -top-3 h-3 w-px bg-gradient-to-t from-border/50 to-transparent" />
 
               {items.map((item, index) => {
-                  const status = getStatus(item.startTime, item.endTime);
-                  const isLive = status === "live";
-                  const isPast = status === "past";
-                  const isLast = index === items.length - 1;
+                const status = getStatus(item.startTime, item.endTime)
+                const isLive = status === "live"
+                const isPast = status === "past"
+                const isLast = index === items.length - 1
 
-                  return (
-                    <div key={item.id} className="relative pl-8 py-2 first:pt-0 last:pb-0 group">
-                       {/* Timeline Dot */}
-                      <div className={cn(
-                          "absolute left-[7px] top-[14px] h-2.5 w-2.5 rounded-full border-2 ring-4 ring-background transition-colors z-10",
-                          isLive ? "bg-primary border-primary" : 
-                          isPast ? "bg-muted border-muted-foreground/30" : 
-                          "bg-background border-primary"
-                      )} />
+                return (
+                  <div key={item.id} className="relative pl-8 py-2 first:pt-0 last:pb-0 group">
+                    <div className={cn(
+                      "absolute left-[7px] top-[14px] h-2.5 w-2.5 rounded-full border-2 ring-4 ring-background transition-colors z-10",
+                      isLive ? "bg-primary border-primary" :
+                      isPast ? "bg-muted border-muted-foreground/30" :
+                      "bg-background border-primary"
+                    )} />
 
-                      <Link
-                        href={`/teacher/classes/my/${encodeURIComponent(item.classId)}`}
-                        className={cn(
-                            "block rounded-md border p-2.5 transition-all hover:bg-muted/50",
-                            isLive ? "bg-primary/5 border-primary/50 shadow-sm" : 
-                            isPast ? "opacity-60 grayscale bg-muted/20 border-transparent" : 
-                            "bg-card"
-                        )}
-                      >
-                        <div className="flex items-start justify-between gap-3">
-                          <div className="space-y-0.5 min-w-0">
-                            <div className="flex items-center gap-2">
-                                <span className={cn(
-                                    "font-medium text-sm truncate", 
-                                    isLive ? "text-primary" : "text-foreground"
-                                )}>
-                                  {item.course}
-                                </span>
-                                {isLive && (
-                                    <Badge variant="default" className="h-4 px-1 text-[9px] animate-pulse">
-                                        LIVE
-                                    </Badge>
-                                )}
-                            </div>
-                            <div className="flex items-center gap-1.5 text-xs text-muted-foreground truncate">
-                              <span>{item.className}</span>
-                              {item.location && (
-                                  <>
-                                      <span>·</span>
-                                      <span className="flex items-center">
-                                          <MapPin className="mr-0.5 h-2.5 w-2.5" />
-                                          {item.location}
-                                      </span>
-                                  </>
-                              )}
-                            </div>
+                    <Link
+                      href={`/teacher/classes/my/${encodeURIComponent(item.classId)}`}
+                      className={cn(
+                        "block rounded-md border p-2.5 transition-all hover:bg-muted/50",
+                        isLive ? "bg-primary/5 border-primary/50 shadow-sm" :
+                        isPast ? "opacity-60 grayscale bg-muted/20 border-transparent" :
+                        "bg-card"
+                      )}
+                    >
+                      <div className="flex items-start justify-between gap-3">
+                        <div className="space-y-0.5 min-w-0">
+                          <div className="flex items-center gap-2">
+                            <span className={cn(
+                              "font-medium text-sm truncate",
+                              isLive ? "text-primary" : "text-foreground"
+                            )}>
+                              {item.course}
+                            </span>
+                            {isLive && (
+                              <Badge variant="default" className="h-4 px-1 text-[9px] animate-pulse">
+                                {t("badge.live")}
+                              </Badge>
+                            )}
                           </div>
-                          
-                          <div className={cn(
-                              "text-right text-xs font-medium tabular-nums whitespace-nowrap",
-                              isLive ? "text-primary" : "text-muted-foreground"
-                          )}>
-                              {item.startTime}
-                              <span className="text-[10px] opacity-70 ml-0.5">– {item.endTime}</span>
+                          <div className="flex items-center gap-1.5 text-xs text-muted-foreground truncate">
+                            <span>{item.className}</span>
+                            {item.location && (
+                              <>
+                                <span>·</span>
+                                <span className="flex items-center">
+                                  <MapPin className="mr-0.5 h-2.5 w-2.5" />
+                                  {item.location}
+                                </span>
+                              </>
+                            )}
                           </div>
                         </div>
-                      </Link>
-                      
-                      {/* Connection Line to Next (if not last) */}
-                      {!isLast && (
-                          <div className="absolute left-[11px] top-[24px] bottom-[-8px] w-px bg-border" />
-                      )}
-                    </div>
-                  );
+
+                        <div className={cn(
+                          "text-right text-xs font-medium tabular-nums whitespace-nowrap",
+                          isLive ? "text-primary" : "text-muted-foreground"
+                        )}>
+                          {item.startTime}
+                          <span className="text-[10px] opacity-70 ml-0.5">– {item.endTime}</span>
+                        </div>
+                      </div>
+                    </Link>
+
+                    {!isLast && (
+                      <div className="absolute left-[11px] top-[24px] bottom-[-8px] w-px bg-border" />
+                    )}
+                  </div>
+                )
               })}
-              
-              {/* Bottom Hint */}
+
               {items.length > 3 ? (
-                  <div className="text-[10px] text-center text-muted-foreground pt-2 pb-1 opacity-50">
-                      Scroll for more
-                  </div>
+                <div className="text-[10px] text-center text-muted-foreground pt-2 pb-1 opacity-50">
+                  {t("schedule.scrollForMore")}
+                </div>
               ) : (
-                  <div className="text-[10px] text-center text-muted-foreground pt-4 pb-1 opacity-50 italic">
-                      No more classes today
-                  </div>
+                <div className="text-[10px] text-center text-muted-foreground pt-4 pb-1 opacity-50 italic">
+                  {t("schedule.noMoreClasses")}
+                </div>
               )}
             </div>
           </ScrollArea>
         )}
       </CardContent>
     </Card>
-  );
+  )
 }