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/assignments/create/page.tsx

@@ -0,0 +1,31 @@
+import { HomeworkAssignmentForm } from "@/modules/homework/components/homework-assignment-form"
+import { getExams } from "@/modules/exams/data-access"
+import { EmptyState } from "@/shared/components/ui/empty-state"
+import { FileQuestion } from "lucide-react"
+
+export default async function CreateHomeworkAssignmentPage() {
+  const exams = await getExams({})
+  const options = exams.map((e) => ({ id: e.id, title: e.title }))
+
+  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">Create Assignment</h2>
+          <p className="text-muted-foreground">Dispatch homework from an existing exam.</p>
+        </div>
+      </div>
+
+      {options.length === 0 ? (
+        <EmptyState
+          title="No exams available"
+          description="Create an exam first, then dispatch it as homework."
+          icon={FileQuestion}
+          action={{ label: "Create Exam", href: "/teacher/exams/create" }}
+        />
+      ) : (
+        <HomeworkAssignmentForm exams={options} />
+      )}
+    </div>
+  )
+}