feat(classes): optimize teacher dashboard ui and implement grade management

src/shared/db/relations.ts

@@ -15,6 +15,7 @@ import {
   classes,
   classEnrollments,
   classSchedule,
+  subjects,
   exams, 
   examQuestions, 
   examSubmissions, 
@@ -88,8 +89,8 @@ export const questionsRelations = relations(questions, ({ one, many }) => ({
     relationName: "question_hierarchy",
   }),
   
-  // Many-to-Many with Knowledge Points
-  questionsToKnowledgePoints: many(questionsToKnowledgePoints),
+  // Many-to-Many with Knowledge Points (Direct relation mapping)
+  knowledgePoints: many(questionsToKnowledgePoints),
   
   // Usage in Exams
   examQuestions: many(examQuestions),
@@ -209,6 +210,14 @@ export const examsRelations = relations(exams, ({ one, many }) => ({
     fields: [exams.creatorId],
     references: [users.id],
   }),
+  subject: one(subjects, {
+    fields: [exams.subjectId],
+    references: [subjects.id],
+  }),
+  gradeEntity: one(grades, {
+    fields: [exams.gradeId],
+    references: [grades.id],
+  }),
   questions: many(examQuestions),
   submissions: many(examSubmissions),
 }));

src/shared/db/schema.ts

@@ -184,6 +184,17 @@ export const questionsToKnowledgePoints = mysqlTable("questions_to_knowledge_poi
 
 // --- 4. Academic / Teaching Flow ---
 
+export const subjects = mysqlTable("subjects", {
+  id: id("id").primaryKey(),
+  name: varchar("name", { length: 100 }).notNull().unique(),
+  code: varchar("code", { length: 50 }).unique(),
+  order: int("order").default(0),
+  createdAt: timestamp("created_at").defaultNow().notNull(),
+  updatedAt: timestamp("updated_at").defaultNow().onUpdateNow().notNull(),
+}, (table) => ({
+  nameIdx: index("subjects_name_idx").on(table.name),
+}));
+
 export const textbooks = mysqlTable("textbooks", {
   id: id("id").primaryKey(),
   title: varchar("title", { length: 255 }).notNull(),
@@ -406,6 +417,10 @@ export const exams = mysqlTable("exams", {
   
   creatorId: varchar("creator_id", { length: 128 }).notNull().references(() => users.id),
   
+  // Link to Subjects and Grades
+  subjectId: varchar("subject_id", { length: 128 }).references(() => subjects.id),
+  gradeId: varchar("grade_id", { length: 128 }).references(() => grades.id),
+
   startTime: timestamp("start_time"),
   endTime: timestamp("end_time"),
   
@@ -414,7 +429,10 @@ export const exams = mysqlTable("exams", {
   
   createdAt: timestamp("created_at").defaultNow().notNull(),
   updatedAt: timestamp("updated_at").defaultNow().onUpdateNow().notNull(),
-});
+}, (table) => ({
+  subjectIdx: index("exams_subject_idx").on(table.subjectId),
+  gradeIdx: index("exams_grade_idx").on(table.gradeId),
+}));
 
 // Linking Exams to Questions (Many-to-Many often, or One-to-Many if specific to exam)
 // Usually questions are reused, so Many-to-Many