Add network map UX and theme support.

Introduce network map view/components with filtering and positioning, expand contacts/map backend fields and migrations, and add a persistent light/dark theme toggle with graph label color updates for readability.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/contacts/migrations/0004_contact_map_default_off.py

@@ -0,0 +1,21 @@
+from django.db import migrations
+
+
+def set_map_false_for_all(apps, schema_editor):
+    Contact = apps.get_model('contacts', 'Contact')
+    Contact.objects.all().update(include_on_network_map=False)
+
+
+def noop_reverse(apps, schema_editor):
+    pass
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('contacts', '0003_contact_include_on_network_map'),
+    ]
+
+    operations = [
+        migrations.RunPython(set_map_false_for_all, noop_reverse),
+    ]