feat: add JWT auth foundation - /api/v1/ with admin login, refresh, me, health endpoints

- Add djangorestframework-simplejwt==5.3.1 to requirements-docker.txt
- Configure REST_FRAMEWORK with JWTAuthentication and SIMPLE_JWT settings
- Create admin_api Django app with AdminLoginView, MeView, HealthView
- Wire /api/v1/ routes without touching existing /api/ mobile endpoints
- Resolve pre-existing events migration conflict (0010_merge)
- Superuser admin created for initial authentication

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin_api/serializers.py

@@ -0,0 +1,18 @@
+from rest_framework import serializers
+from django.contrib.auth import get_user_model
+User = get_user_model()
+
+class UserSerializer(serializers.ModelSerializer):
+    name = serializers.SerializerMethodField()
+    role = serializers.SerializerMethodField()
+    class Meta:
+        model = User
+        fields = ['id', 'email', 'username', 'name', 'role']
+    def get_name(self, obj):
+        return f"{obj.first_name} {obj.last_name}".strip() or obj.username
+    def get_role(self, obj):
+        if obj.is_superuser:
+            return 'superadmin'
+        if obj.is_staff:
+            return 'admin'
+        return getattr(obj, 'role', 'user')