已完成“成绩管理与学业档案”模块：

教师批量录入平时、期中、期末成绩。
自动计算总评、绩点和及格状态。
支持缺考、缓考、免修。
教师提交 → 学院审核/退回 → 校级发布。
学生只能查看正式发布成绩。
自动统计平均分、完成度、及格率和加权 GPA。
SQLite 本地增量升级和 MySQL 正式迁移均已完成。
分级权限在前后端同时校验。

src/Jiaowu.Api/Infrastructure/Grades/GradeCalculator.cs

@@ -0,0 +1,57 @@
+using Jiaowu.Api.Domain.Academic;
+
+namespace Jiaowu.Api.Infrastructure.Grades;
+
+public static class GradeCalculator
+{
+    public static bool AreWeightsValid(
+        decimal regularWeight,
+        decimal midtermWeight,
+        decimal finalWeight) =>
+        regularWeight is >= 0 and <= 100 &&
+        midtermWeight is >= 0 and <= 100 &&
+        finalWeight is >= 0 and <= 100 &&
+        regularWeight + midtermWeight + finalWeight == 100;
+
+    public static decimal? CalculateTotal(
+        decimal? regularScore,
+        decimal? midtermScore,
+        decimal? finalScore,
+        decimal regularWeight,
+        decimal midtermWeight,
+        decimal finalWeight,
+        GradeExamStatus examStatus)
+    {
+        if (examStatus != GradeExamStatus.Normal ||
+            regularWeight > 0 && !regularScore.HasValue ||
+            midtermWeight > 0 && !midtermScore.HasValue ||
+            finalWeight > 0 && !finalScore.HasValue)
+        {
+            return null;
+        }
+
+        var total =
+            (regularScore ?? 0) * regularWeight / 100 +
+            (midtermScore ?? 0) * midtermWeight / 100 +
+            (finalScore ?? 0) * finalWeight / 100;
+        return Math.Round(total, 1, MidpointRounding.AwayFromZero);
+    }
+
+    public static decimal? CalculateGradePoint(decimal? totalScore)
+    {
+        if (!totalScore.HasValue) return null;
+        return totalScore.Value switch
+        {
+            >= 90 => 4.0m,
+            >= 85 => 3.7m,
+            >= 82 => 3.3m,
+            >= 78 => 3.0m,
+            >= 75 => 2.7m,
+            >= 72 => 2.3m,
+            >= 68 => 2.0m,
+            >= 64 => 1.5m,
+            >= 60 => 1.0m,
+            _ => 0m
+        };
+    }
+}