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/es/children.json

@@ -0,0 +1,29 @@
+{
+  "title": "Niños",
+  "subtitle": "Gestiona los perfiles de los niños de tu familia",
+  "addChild": "Agregar Niño",
+  "addFirstChild": "Agregar Primer Niño",
+  "editChild": "Editar Niño",
+  "deleteChild": "Eliminar Niño",
+  "noChildren": "Aún no se han agregado niños",
+  "noChildrenSubtitle": "Agrega tu primer niño para comenzar a rastrear sus actividades",
+  "age": "Edad",
+  "gender": {
+    "male": "Masculino",
+    "female": "Femenino",
+    "other": "Otro"
+  },
+  "errors": {
+    "noFamily": "No se encontró familia. Por favor completa la incorporación primero.",
+    "loadFailed": "Error al cargar niños",
+    "saveFailed": "Error al guardar niño",
+    "deleteFailed": "Error al eliminar niño",
+    "noFamilyId": "No se encontró ID de familia"
+  },
+  "ageFormat": {
+    "year": "año",
+    "years": "años",
+    "month": "mes",
+    "months": "meses"
+  }
+}

maternal-web/locales/es/tracking.json

@@ -1,5 +1,14 @@
 {
-  "title": "Activity Tracking",
+  "title": "Seguimiento de Actividades",
+  "trackActivity": "Registrar Actividad",
+  "selectActivity": "Selecciona una actividad para registrar",
+  "activities": {
+    "feeding": "Alimentación",
+    "sleep": "Sueño",
+    "diaper": "Pañal",
+    "medicine": "Medicina",
+    "activity": "Actividad"
+  },
   "feeding": {
     "title": "Feeding",
     "addFeeding": "Add Feeding",