feat: Apply localization to Track and Children pages (Phase 9 - Batch 2)

**Pages Localized:**
- Track main page: Activity selection menu with all tracking options
- Children page: Complete localization including age formatting with pluralization

**Translation Files:**
- Enhanced tracking.json: Added trackActivity, selectActivity, and activities keys
- Created children.json for all 5 languages with comprehensive strings
- Updated i18n config to include children namespace

**Key Features:**
- Localized age calculation with proper pluralization (year/years, month/months)
- All error messages translated
- Gender labels localized
- Properly formatted age display for all languages

**Languages Supported:**
- English, Spanish, French, Portuguese, Chinese (Simplified)

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

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

maternal-web/locales/fr/children.json

@@ -0,0 +1,29 @@
+{
+  "title": "Enfants",
+  "subtitle": "Gérez les profils des enfants de votre famille",
+  "addChild": "Ajouter un Enfant",
+  "addFirstChild": "Ajouter le Premier Enfant",
+  "editChild": "Modifier l'Enfant",
+  "deleteChild": "Supprimer l'Enfant",
+  "noChildren": "Aucun enfant ajouté pour le moment",
+  "noChildrenSubtitle": "Ajoutez votre premier enfant pour commencer à suivre ses activités",
+  "age": "Âge",
+  "gender": {
+    "male": "Masculin",
+    "female": "Féminin",
+    "other": "Autre"
+  },
+  "errors": {
+    "noFamily": "Aucune famille trouvée. Veuillez d'abord terminer l'intégration.",
+    "loadFailed": "Échec du chargement des enfants",
+    "saveFailed": "Échec de l'enregistrement de l'enfant",
+    "deleteFailed": "Échec de la suppression de l'enfant",
+    "noFamilyId": "Aucun ID de famille trouvé"
+  },
+  "ageFormat": {
+    "year": "an",
+    "years": "ans",
+    "month": "mois",
+    "months": "mois"
+  }
+}