feat: Complete comprehensive localization of all tracking and management pages

- Feeding page: 47+ strings localized with validation, success/error messages
- Medicine page: 44 strings localized with unit conversion support
- Sleep page: Already localized (verified)
- Diaper page: Already localized (verified)
- Activity page: Already localized (verified)
- AI Assistant: 51 strings localized including chat interface and suggested questions
- Children page: 38 strings fully localized with gender labels
- Family page: 42 strings localized with role management
- Insights page: 41 strings localized including charts and analytics

Added translation files:
- locales/en/ai.json (44 keys)
- locales/en/family.json (42 keys)
- locales/en/insights.json (41 keys)

Updated translation files:
- locales/en/tracking.json (added feeding, health/medicine sections)
- locales/en/children.json (verified complete)

All pages now use useTranslation hook with proper namespaces.
All user-facing text externalized and ready for multi-language support.

maternal-web/app/children/page.tsx

@@ -239,7 +239,7 @@ export default function ChildrenPage() {
                               {child.name}
                             </Typography>
                             <Chip
-                              label={child.gender}
+                              label={t(`gender.${child.gender}`)}
                               size="small"
                               sx={{ textTransform: 'capitalize', mt: 0.5 }}
                             />