fix: Correct database table and column names in analytics queries

- Changed 'devices' to 'device_registry' in getDeviceDistribution
- Changed 'date_of_birth' to 'birth_date' in getAgeDistribution
- Added deleted_at filter to exclude deleted children
- Added proper ordering to age distribution results

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

maternal-app/maternal-app-backend/src/modules/admin/dashboard/dashboard.service.ts

@@ -111,7 +111,7 @@ export class DashboardService {
           ELSE 'Web'
         END as name,
         COUNT(*) * 100.0 / SUM(COUNT(*)) OVER () as value
-      FROM devices
+      FROM device_registry
       GROUP BY platform`,
     );
 
@@ -163,12 +163,21 @@ export class DashboardService {
         END as age,
         COUNT(*) as count
       FROM (
-        SELECT EXTRACT(YEAR FROM AGE(date_of_birth)) * 12 + EXTRACT(MONTH FROM AGE(date_of_birth)) as age_months
+        SELECT EXTRACT(YEAR FROM AGE(birth_date)) * 12 + EXTRACT(MONTH FROM AGE(birth_date)) as age_months
         FROM children
-        WHERE date_of_birth IS NOT NULL
+        WHERE birth_date IS NOT NULL AND deleted_at IS NULL
       ) ages
       GROUP BY age
-      ORDER BY age`,
+      ORDER BY
+        CASE age
+          WHEN '0-6 months' THEN 1
+          WHEN '6-12 months' THEN 2
+          WHEN '1-2 years' THEN 3
+          WHEN '2-3 years' THEN 4
+          WHEN '3-4 years' THEN 5
+          WHEN '4-5 years' THEN 6
+          ELSE 7
+        END`,
     );
 
     return result.map((row: any) => ({