重构作业结构：优化实体模型、DTO映射和前端界面

- 重构AppMainStruct、AssignmentQuestion、Question等实体模型
- 更新相关DTO以匹配新的数据结构
- 优化前端页面布局和组件
- 添加全局信息和笔记功能相关代码
- 更新数据库迁移和程序配置

TechHelper.Client/Pages/Student/BaseInfoCard/StudentSubmissionPreviewTableCard_MudCard_NoUSE.razor

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+@using MudBlazor
+@using System.Collections.Generic
+
+<MudDataGrid Items="@Elements.Take(4)" Hover="@_hover" Dense="@_dense" Striped="@_striped" Bordered="@_bordered"
+             RowStyleFunc="@_rowStyleFunc" RowClass="my-2 rounded-xl">
+    <Columns >
+        <PropertyColumn Property="x => x.Number" Title="Nr" />
+        <PropertyColumn Property="x => x.Sign" />
+        <PropertyColumn Property="x => x.Name" CellStyleFunc="@_cellStyleFunc" />
+        <PropertyColumn Property="x => x.Position" />
+        <PropertyColumn Property="x => x.Molar" Title="Molar mass" />
+    </Columns>
+</MudDataGrid>
+
+<div class="d-flex flex-wrap mt-4">
+    <MudSwitch @bind-Value="_hover" Color="Color.Primary">Hover</MudSwitch>
+    <MudSwitch @bind-Value="_dense" Color="Color.Secondary">Dense</MudSwitch>
+    <MudSwitch @bind-Value="_striped" Color="Color.Tertiary">Striped</MudSwitch>
+    <MudSwitch @bind-Value="_bordered" Color="Color.Warning">Bordered</MudSwitch>
+</div>
+
+@code {
+    // Element类定义
+    public class Element
+    {
+        public int Number { get; set; }
+        public string Sign { get; set; }
+        public string Name { get; set; }
+        public int Position { get; set; }
+        public decimal Molar { get; set; }
+    }
+
+    // 示例数据
+    private IEnumerable<Element> Elements = new List<Element>
+    {
+        new Element { Number = 1, Sign = "H", Name = "Hydrogen", Position = 1, Molar = 1.008m },
+        new Element { Number = 2, Sign = "He", Name = "Helium", Position = 0, Molar = 4.0026m },
+        new Element { Number = 3, Sign = "Li", Name = "Lithium", Position = 1, Molar = 6.94m },
+        new Element { Number = 4, Sign = "Be", Name = "Beryllium", Position = 2, Molar = 9.0122m },
+        new Element { Number = 5, Sign = "B", Name = "Boron", Position = 13, Molar = 10.81m }
+    };
+
+    private bool _hover;
+    private bool _dense;
+    private bool _striped;
+    private bool _bordered;
+
+    // 行样式函数：Position为0的行显示为斜体
+    private Func<Element, int, string> _rowStyleFunc => (x, i) =>
+    {
+        if (x.Position == 0)
+            return "font-style:italic";
+
+        return "";
+    };
+
+    // 单元格样式函数：根据元素编号设置背景色，根据摩尔质量设置字体粗细
+    private Func<Element, string> _cellStyleFunc => x =>
+    {
+        string style = "";
+
+        if (x.Number == 1)
+            style += "background-color:#8CED8C"; // 浅绿色
+
+        else if (x.Number == 2)
+            style += "background-color:#E5BDE5"; // 浅紫色
+
+        else if (x.Number == 3)
+            style += "background-color:#EACE5D"; // 浅黄色
+
+        else if (x.Number == 4)
+            style += "background-color:#F1F165"; // 浅黄色
+
+        if (x.Molar > 5)
+            style += ";font-weight:bold";
+
+        return style;
+    };
+}