feat(student): 完成 student 模块 v4 剩余修复

- P1-4.2: 新增班级详情页 courses/[classId]，展示教师/学校/教室信息与课表

- P2-2.5: 今日课表卡片高亮当前/下一节课（useMemo 实时计算）

- P2-3.9: 作业作答进度网格支持点击跳转题目（scrollIntoView）

- P2-3.10: 作业复习视图显示正确答案（选择/判断/文本题）

- P2-4.4: 课程列表支持按班级名/教师/学校搜索

- P2-5.2: 成绩页新增趋势折线图组件 GradeTrendCard

- P2-9.2/9.3: 诊断报告新增历史记录卡片与弱点练习入口

- P2-10.2: 选课列表支持搜索与选课模式筛选

- P2-11.3: 修复教材阅读页全屏溢出

- P3-1.5: 面包屑保留首个角色段作为根上下文

- P3-7.3: 课表项支持点击跳转至班级详情页（ScheduleList href）

src/modules/grades/components/grade-trend-card.tsx

@@ -0,0 +1,57 @@
+"use client"
+
+import { useMemo } from "react"
+import { BarChart3 } from "lucide-react"
+
+import { ChartCardShell } from "@/shared/components/charts/chart-card-shell"
+import { TrendLineChart } from "@/shared/components/charts/trend-line-chart"
+import { formatDate } from "@/shared/lib/utils"
+import type { StudentGradeSummary } from "../types"
+
+export function GradeTrendCard({ summary }: { summary: StudentGradeSummary }) {
+  const chartData = useMemo(() => {
+    return [...summary.records]
+      .sort((a, b) => new Date(a.createdAt).getTime() - new Date(b.createdAt).getTime())
+      .map((r) => ({
+        title: r.title,
+        score: Math.round((r.score / r.fullScore) * 100),
+        fullTitle: r.title,
+        submittedAt: formatDate(r.createdAt),
+        rawScore: r.score,
+        maxScore: r.fullScore,
+      }))
+  }, [summary.records])
+
+  const hasData = chartData.length > 0
+
+  return (
+    <ChartCardShell
+      title="Grade Trend"
+      icon={BarChart3}
+      iconClassName="text-muted-foreground"
+      isEmpty={!hasData}
+      emptyTitle="No grade records yet"
+      emptyDescription="Your grade trend will appear here once records are added."
+      emptyClassName="h-64"
+    >
+      <div className="rounded-md border bg-card p-4">
+        <TrendLineChart
+          data={chartData}
+          series={[
+            {
+              dataKey: "score",
+              name: "Score (%)",
+              color: "hsl(var(--primary))",
+              dotRadius: 4,
+              activeDotRadius: 6,
+            },
+          ]}
+          heightClassName="h-[240px]"
+          margin={{ left: 12, right: 12, top: 12, bottom: 12 }}
+          yWidth={30}
+          tooltipClassName="w-[200px]"
+        />
+      </div>
+    </ChartCardShell>
+  )
+}