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/homework/submissions/page.tsx

@@ -1,7 +1,22 @@
+import Link from "next/link"
 import { EmptyState } from "@/shared/components/ui/empty-state"
+import { Badge } from "@/shared/components/ui/badge"
+import {
+  Table,
+  TableBody,
+  TableCell,
+  TableHead,
+  TableHeader,
+  TableRow,
+} from "@/shared/components/ui/table"
+import { formatDate } from "@/shared/lib/utils"
+import { getHomeworkSubmissions } from "@/modules/homework/data-access"
 import { Inbox } from "lucide-react"
 
-export default function SubmissionsPage() {
+export default async function SubmissionsPage() {
+  const submissions = await getHomeworkSubmissions()
+  const hasSubmissions = submissions.length > 0
+
   return (
     <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
       <div className="flex items-center justify-between space-y-2">
@@ -12,11 +27,48 @@ export default function SubmissionsPage() {
           </p>
         </div>
       </div>
-      <EmptyState
-        title="No submissions"
-        description="There are no homework submissions to review."
-        icon={Inbox}
-      />
+
+      {!hasSubmissions ? (
+        <EmptyState
+          title="No submissions"
+          description="There are no homework submissions to review."
+          icon={Inbox}
+        />
+      ) : (
+        <div className="rounded-md border bg-card">
+          <Table>
+            <TableHeader>
+              <TableRow>
+                <TableHead>Assignment</TableHead>
+                <TableHead>Student</TableHead>
+                <TableHead>Status</TableHead>
+                <TableHead>Submitted</TableHead>
+                <TableHead>Score</TableHead>
+              </TableRow>
+            </TableHeader>
+            <TableBody>
+              {submissions.map((s) => (
+                <TableRow key={s.id}>
+                  <TableCell className="font-medium">
+                    <Link href={`/teacher/homework/submissions/${s.id}`} className="hover:underline">
+                      {s.assignmentTitle}
+                    </Link>
+                  </TableCell>
+                  <TableCell>{s.studentName}</TableCell>
+                  <TableCell>
+                    <Badge variant="outline" className="capitalize">
+                      {s.status}
+                    </Badge>
+                    {s.isLate ? <span className="ml-2 text-xs text-destructive">Late</span> : null}
+                  </TableCell>
+                  <TableCell className="text-muted-foreground">{s.submittedAt ? formatDate(s.submittedAt) : "-"}</TableCell>
+                  <TableCell>{typeof s.score === "number" ? s.score : "-"}</TableCell>
+                </TableRow>
+              ))}
+            </TableBody>
+          </Table>
+        </div>
+      )}
     </div>
   )
 }