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)/student/learning/assignments/[assignmentId]/page.tsx

@@ -0,0 +1,34 @@
+import { notFound } from "next/navigation"
+
+import { getDemoStudentUser, getStudentHomeworkTakeData } from "@/modules/homework/data-access"
+import { HomeworkTakeView } from "@/modules/homework/components/homework-take-view"
+import { formatDate } from "@/shared/lib/utils"
+
+export default async function StudentAssignmentTakePage({
+  params,
+}: {
+  params: Promise<{ assignmentId: string }>
+}) {
+  const { assignmentId } = await params
+  const student = await getDemoStudentUser()
+  if (!student) return notFound()
+
+  const data = await getStudentHomeworkTakeData(assignmentId, student.id)
+  if (!data) return notFound()
+
+  return (
+    <div className="flex h-full flex-col space-y-4 p-6">
+      <div className="flex flex-col gap-1">
+        <h2 className="text-2xl font-bold tracking-tight">{data.assignment.title}</h2>
+        <div className="text-sm text-muted-foreground">
+          <span>Due: {data.assignment.dueAt ? formatDate(data.assignment.dueAt) : "-"}</span>
+          <span className="mx-2">•</span>
+          <span>Max Attempts: {data.assignment.maxAttempts}</span>
+        </div>
+      </div>
+
+      <HomeworkTakeView assignmentId={data.assignment.id} initialData={data} />
+    </div>
+  )
+}
+