feat: home page with MUI components

- Rewrote frontend from JSX to TypeScript (TSX)
- AppLayout with MUI AppBar, ThemeProvider, CssBaseline
- HomePage at / with dashboard metrics and recent updates
- MetricsPanel with 4 metric cards (total, interviews, offers, rejection rate)
- UpdateCard for each job update with status chip
- LoadingSkeleton during data fetch
- Error Alert on API failure
- Create New Job Application button navigating to /applications/new
- Vite proxy for /api → backend on :8000
- useDashboardData custom hook with concurrent fetch

Closes #2

api/jobs/serializers.py

@@ -0,0 +1,45 @@
+from rest_framework import serializers
+
+from .models import JobApplication, JobUpdate
+
+
+class JobUpdateSerializer(serializers.ModelSerializer):
+    company_name = serializers.CharField(source="job_application.company_name", read_only=True)
+    position_title = serializers.CharField(source="job_application.position_title", read_only=True)
+    job_id = serializers.IntegerField(source="job_application.id", read_only=True)
+
+    class Meta:
+        model = JobUpdate
+        fields = [
+            "id",
+            "job_id",
+            "company_name",
+            "position_title",
+            "from_status",
+            "to_status",
+            "notes",
+            "created_at",
+            "metrics",
+        ]
+
+
+class JobApplicationSerializer(serializers.ModelSerializer):
+    class Meta:
+        model = JobApplication
+        fields = [
+            "id",
+            "company_name",
+            "position_title",
+            "status",
+            "notes",
+            "created_at",
+            "updated_at",
+        ]
+
+
+class DashboardMetricsSerializer(serializers.Serializer):
+    total_applications = serializers.IntegerField()
+    status_breakdown = serializers.DictField(child=serializers.IntegerField())
+    interviews_count = serializers.IntegerField()
+    offers_count = serializers.IntegerField()
+    rejection_rate = serializers.FloatField()