test(mocks): update exam mock data

- Update src/mocks/exam-data.ts with new mock entries

src/mocks/exam-data.ts

@@ -5,6 +5,7 @@ export let MOCK_EXAMS: Exam[] = [
     id: "exam_001",
     title: "Algebra Midterm",
     subject: "Mathematics",
+    subjectId: "subj_math",
     grade: "Grade 10",
     status: "draft",
     difficulty: 3,
@@ -19,6 +20,7 @@ export let MOCK_EXAMS: Exam[] = [
     id: "exam_002",
     title: "Physics Mechanics Quiz",
     subject: "Physics",
+    subjectId: "subj_physics",
     grade: "Grade 11",
     status: "published",
     difficulty: 4,
@@ -33,6 +35,7 @@ export let MOCK_EXAMS: Exam[] = [
     id: "exam_003",
     title: "English Reading Comprehension",
     subject: "English",
+    subjectId: "subj_english",
     grade: "Grade 12",
     status: "published",
     difficulty: 2,
@@ -47,6 +50,7 @@ export let MOCK_EXAMS: Exam[] = [
     id: "exam_004",
     title: "Chemistry Final",
     subject: "Chemistry",
+    subjectId: "subj_chemistry",
     grade: "Grade 12",
     status: "archived",
     difficulty: 5,
@@ -61,6 +65,7 @@ export let MOCK_EXAMS: Exam[] = [
     id: "exam_005",
     title: "Geometry Chapter Test",
     subject: "Mathematics",
+    subjectId: "subj_math",
     grade: "Grade 9",
     status: "published",
     difficulty: 3,