Merge exams grading into homework

Redirect /teacher/exams/grading* to /teacher/homework/submissions; remove exam grading UI/actions/data-access; add homework student workflow and update design docs.

src/modules/exams/data-access.ts

@@ -1,5 +1,5 @@
 import { db } from "@/shared/db"
-import { exams, examQuestions, examSubmissions, submissionAnswers } from "@/shared/db/schema"
+import { exams } from "@/shared/db/schema"
 import { eq, desc, like, and, or } from "drizzle-orm"
 import { cache } from "react"
 
@@ -137,82 +137,3 @@ export const getExamById = cache(async (id: string) => {
     })),
   }
 })
-
-export const getExamSubmissions = cache(async () => {
-  const data = await db.query.examSubmissions.findMany({
-    orderBy: [desc(examSubmissions.submittedAt)],
-    with: {
-      exam: true,
-      student: true
-    }
-  })
-
-  return data.map(sub => ({
-    id: sub.id,
-    examId: sub.examId,
-    examTitle: sub.exam.title,
-    studentName: sub.student.name || "Unknown",
-    submittedAt: sub.submittedAt ? sub.submittedAt.toISOString() : new Date().toISOString(),
-    score: sub.score || undefined,
-    status: sub.status as "pending" | "graded",
-  }))
-})
-
-export const getSubmissionDetails = cache(async (submissionId: string) => {
-  const submission = await db.query.examSubmissions.findFirst({
-    where: eq(examSubmissions.id, submissionId),
-    with: {
-      student: true,
-      exam: true,
-    }
-  })
-
-  if (!submission) return null
-
-  // Fetch answers
-  const answers = await db.query.submissionAnswers.findMany({
-    where: eq(submissionAnswers.submissionId, submissionId),
-    with: {
-      question: true
-    }
-  })
-
-  // Fetch exam questions structure (to know max score and order)
-  const examQ = await db.query.examQuestions.findMany({
-    where: eq(examQuestions.examId, submission.examId),
-    orderBy: [desc(examQuestions.order)],
-  })
-
-  type QuestionContent = { text?: string } & Record<string, unknown>
-
-  const toQuestionContent = (v: unknown): QuestionContent | null => {
-    if (!isRecord(v)) return null
-    return v as QuestionContent
-  }
-
-  // Map answers with question details
-  const answersWithDetails = answers.map(ans => {
-    const eqRel = examQ.find(q => q.questionId === ans.questionId)
-    return {
-      id: ans.id,
-      questionId: ans.questionId,
-      questionContent: toQuestionContent(ans.question.content),
-      questionType: ans.question.type,
-      maxScore: eqRel?.score || 0,
-      studentAnswer: ans.answerContent,
-      score: ans.score,
-      feedback: ans.feedback,
-      order: eqRel?.order || 0
-    }
-  }).sort((a, b) => a.order - b.order)
-
-  return {
-    id: submission.id,
-    studentName: submission.student.name || "Unknown",
-    examTitle: submission.exam.title,
-    submittedAt: submission.submittedAt ? submission.submittedAt.toISOString() : null,
-    status: submission.status,
-    totalScore: submission.score,
-    answers: answersWithDetails
-  }
-})