feat(#49): add geolocation (latitude/longitude) to municipalities

- Municipality model with optional latitude/longitude decimal fields
- Municipality and brief serializers expose lat/lng (also in product_provenance of public/authenticated summaries for the Leaflet map)
- seed_geography endpoint reads lat/lng and updates existing municipalities on reseed (idempotent)
- TDD tests for model, serializers, summaries and seed

tienda_ilusion/don_confiao/serializers/geography.py

@@ -24,7 +24,7 @@ class DepartmentBriefSerializer(serializers.ModelSerializer):
 class MunicipalityBriefSerializer(serializers.ModelSerializer):
     class Meta:
         model = Municipality
-        fields = ["id", "name"]
+        fields = ["id", "name", "latitude", "longitude"]
 
 
 class DepartmentSerializer(serializers.ModelSerializer):
@@ -43,4 +43,13 @@ class MunicipalitySerializer(serializers.ModelSerializer):
 
     class Meta:
         model = Municipality
-        fields = ["id", "name", "department", "department_detail", "country", "country_detail"]
+        fields = [
+            "id",
+            "name",
+            "department",
+            "department_detail",
+            "country",
+            "country_detail",
+            "latitude",
+            "longitude",
+        ]