feat: add edit button for ICS subscriptions (#100)

Adds a pencil-icon edit button to each ICS subscription row. Clicking it
opens a modal to update name, color, and shared visibility via PATCH
/calendar/subscriptions/:id. Adds updatedToast i18n key to all 15 locales.

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

public/locales/ar.json

@@ -732,7 +732,8 @@
       "badges": {
         "private": "خاص",
         "shared": "مشترك"
-      }
+      },
+      "updatedToast": "تم تحديث الاشتراك."
     },
     "memberPhoneLabel": "رقم الهاتف (اختياري)",
     "memberEmailLabel": "البريد الإلكتروني (اختياري)",
@@ -897,4 +898,4 @@
   "emptyHint": {
     "recipes": "أنشئ وصفات واربطها بمخطط الوجبات."
   }
-}
+}