feat: merge event charts with metric toggle, add pie chart option to events and channels

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/locales/ar.json

@@ -137,6 +137,8 @@
     "addFirst": "أضف شريحتك الأولى",
     "slideTitle": "عنوان الشريحة",
     "chartType": "نوع الرسم البياني",
+    "bar": "أعمدة",
+    "pie": "دائري",
     "metric": "المقياس",
     "startDate": "تاريخ البداية",
     "endDate": "تاريخ النهاية",

src/locales/en.json

@@ -137,6 +137,8 @@
     "addFirst": "Add your first slide",
     "slideTitle": "Slide Title",
     "chartType": "Chart Type",
+    "bar": "Bar",
+    "pie": "Pie",
     "metric": "Metric",
     "startDate": "Start Date",
     "endDate": "End Date",