fix(spp_demo): optimize _get_leaf_areas to query only leaf areas

Replace the Python-level filter over all areas with a direct ORM query
using the domain [('child_ids', '=', False)], which lets the database
find leaf areas in a single SQL query instead of loading all records
into memory.

Author: jeremi

spp_demo/models/demo_data_generator.py

@@ -168,8 +168,7 @@ def generate_demo_data(self):
             self.members_range_from = self._default_members_range_from()
             self.members_range_to = self._default_members_range_to()
             raise ValidationError(
-                "Members per Group (From) cannot be greater than Members per Group (To)."
-                " Resetting to default values."
+                "Members per Group (From) cannot be greater than Members per Group (To). Resetting to default values."
             )
 
         self.state = "in_progress"
@@ -371,18 +370,13 @@ def _get_leaf_areas(self):
             recordset: spp.area records at the deepest available level
         """
         Area = self.env["spp.area"]
-        all_areas = Area.search([])
-        if not all_areas:
-            return Area.browse()
 
-        # Find the maximum area_level (deepest in hierarchy)
-        max_level = max(all_areas.mapped("area_level"))
+        # Query only leaf areas directly: areas that have no children.
+        # This is a single SQL query rather than loading all areas into memory.
+        leaf_areas = Area.search([("child_ids", "=", False)])
 
-        # Get areas at the deepest level
-        leaf_areas = all_areas.filtered(lambda a: a.area_level == max_level)
-
-        # Fallback: if no areas at max level, use all areas
-        return leaf_areas if leaf_areas else all_areas
+        # Fallback: if no leaf areas found, return all areas
+        return leaf_areas if leaf_areas else Area.search([])
 
     def get_group_vals(self, fake):
         registration_date = self.get_random_date(