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/app/(dashboard)/teacher/exams/grading/page.tsx

@@ -1,22 +1,5 @@
-import { SubmissionDataTable } from "@/modules/exams/components/submission-data-table"
-import { submissionColumns } from "@/modules/exams/components/submission-columns"
-import { getExamSubmissions } from "@/modules/exams/data-access"
+import { redirect } from "next/navigation"
 
 export default async function ExamGradingPage() {
-  const submissions = await getExamSubmissions()
-
-  return (
-    <div className="flex h-full flex-col space-y-8 p-8">
-      <div className="flex items-center justify-between">
-        <div>
-          <h2 className="text-2xl font-bold tracking-tight">Grading</h2>
-          <p className="text-muted-foreground">Grade student exam submissions.</p>
-        </div>
-      </div>
-
-      <div className="rounded-md border bg-card">
-        <SubmissionDataTable columns={submissionColumns} data={submissions} />
-      </div>
-    </div>
-  )
+  redirect("/teacher/homework/submissions")
 }