fix some issues

src/modules/admin/pages/courses/units/AddUnit.jsx

@@ -1,5 +1,5 @@
 import { useEffect, useState } from "react";
-import { useNavigate, useParams } from "react-router-dom";
+import { useNavigate, useParams, useLocation } from "react-router-dom";
 import { useForm } from "react-hook-form";
 import { z } from "zod";
 import { zodResolver } from "@hookform/resolvers/zod";
@@ -35,10 +35,13 @@ function FieldError({ message }) {
 
 export default function AddUnit() {
   const navigate = useNavigate();
+  const location = useLocation();
   const { courseId } = useParams();
   const { createUnit, fetchCourse, course, loading, syncUnitRequirements } = useCourses();
   const { user } = useAuth();
 
+  const backTarget = location.state?.returnTo ?? `/admin/courses/${courseId}/units`;
+
   const [step, setStep] = useState(0);
   const [requirements, setRequirements] = useState([]);
 
@@ -72,7 +75,7 @@ export default function AddUnit() {
     }
 
     bypassOnce();
-    navigate(`/admin/courses/${courseId}/units`);
+    navigate(backTarget);
   };
 
   return (
@@ -86,13 +89,15 @@ export default function AddUnit() {
               type="button"
               variant="ghost"
               size="icon"
-              onClick={() => (step === 0 ? navigate(`/admin/courses/${courseId}/units`) : setStep(0))}
+              onClick={() => (step === 0 ? navigate(backTarget) : setStep(0))}
             >
               <ChevronLeft className="h-4 w-4" />
             </Button>
             <div>
               <h1 className="text-xl font-semibold">Create Unit</h1>
-              <p className="text-sm text-muted-foreground">Add a new unit to this course.</p>
+              <p className="text-sm text-muted-foreground">
+                Creates a new unit in the shared Units Library and attaches it to this course.
+              </p>
             </div>
           </div>
 
@@ -169,7 +174,7 @@ export default function AddUnit() {
             <Button
               type="button"
               variant="outline"
-              onClick={() => (step === 0 ? navigate(`/admin/courses/${courseId}/units`) : setStep(0))}
+              onClick={() => (step === 0 ? navigate(backTarget) : setStep(0))}
               disabled={loading}
             >
               <ChevronLeft className="h-4 w-4 mr-1" />