feat(db): Add performance indexes for DeletionRequest model

- Add composite index (user, status, created_at) for listing queries
- Add index for reviewed_at field for filtering reviewed requests
- Add index for completed_at field for filtering completed requests
- Create migration 1076_add_deletionrequest_performance_indexes
- Expected improvement: list queries <100ms, filter queries <50ms

Addresses: [AI Scanner] Índices de Performance para DeletionRequest
Epic: Migraciones de Base de Datos

Co-authored-by: dawnsystem <42047891+dawnsystem@users.noreply.github.com>

src/documents/migrations/1076_add_deletionrequest_performance_indexes.py

@@ -0,0 +1,55 @@
+# Generated manually for DeletionRequest performance optimization
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+    """
+    Add performance indexes for DeletionRequest model.
+    
+    These indexes optimize common query patterns:
+    - Filtering by user + status + created_at (most common listing query)
+    - Filtering by reviewed_at (for finding reviewed requests)
+    - Filtering by completed_at (for finding completed requests)
+    
+    Expected performance improvement:
+    - List queries: <100ms
+    - Filter queries: <50ms
+    
+    Addresses Issue: [AI Scanner] Índices de Performance para DeletionRequest
+    Epic: Migraciones de Base de Datos
+    """
+
+    dependencies = [
+        ("documents", "1075_add_performance_indexes"),
+    ]
+
+    operations = [
+        # Composite index for user + status + created_at (most common query pattern)
+        # This supports queries like: DeletionRequest.objects.filter(user=user, status='pending').order_by('-created_at')
+        migrations.AddIndex(
+            model_name="deletionrequest",
+            index=models.Index(
+                fields=["user", "status", "created_at"],
+                name="delreq_user_status_created_idx",
+            ),
+        ),
+        # Index for reviewed_at (for filtering reviewed requests)
+        # Supports queries like: DeletionRequest.objects.filter(reviewed_at__isnull=False)
+        migrations.AddIndex(
+            model_name="deletionrequest",
+            index=models.Index(
+                fields=["reviewed_at"],
+                name="delreq_reviewed_at_idx",
+            ),
+        ),
+        # Index for completed_at (for filtering completed requests)
+        # Supports queries like: DeletionRequest.objects.filter(completed_at__isnull=False)
+        migrations.AddIndex(
+            model_name="deletionrequest",
+            index=models.Index(
+                fields=["completed_at"],
+                name="delreq_completed_at_idx",
+            ),
+        ),
+    ]