fix(spp_area, spp_gis_report): move GIS reference data outside classification group to fix labels

Author: emjay0921

spp_area/views/area_base.xml

@@ -61,7 +61,7 @@
                     <field name="level" invisible="1" />
 
                     <!-- Main Information -->
-                    <group>
+                    <group name="main_info">
                         <group string="Basic Information">
                             <field name="code" placeholder="Area Code..." />
                             <field

spp_gis_report/views/area_views.xml

@@ -13,9 +13,13 @@ Part of OpenSPP. See LICENSE file for full copyright and licensing details.
         <field name="inherit_id" ref="spp_area.view_spparea_form" />
         <field name="priority">20</field>
         <field name="arch" type="xml">
-            <!-- Add Reference Data section after area_sqkm field -->
-            <xpath expr="//field[@name='area_sqkm']" position="after">
+            <!-- Add Reference Data section after the main info group -->
+            <xpath expr="//group[@name='main_info']" position="after">
                 <separator string="Reference Data for GIS Reports" />
+                <div class="text-muted small mb-2">
+                    These fields are populated from external sources such as national census data or official estimates.
+                    They are used for normalization in GIS reports (e.g., per-capita or per-household calculations).
+                </div>
                 <group name="gis_reference_data" col="2">
                     <group name="population_group">
                         <field