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/en.json

@@ -732,7 +732,8 @@
       "badges": {
         "private": "Private",
         "shared": "Shared"
-      }
+      },
+      "updatedToast": "Subscription updated."
     },
     "memberPhoneLabel": "Phone number (optional)",
     "memberEmailLabel": "Email (optional)",
@@ -916,4 +917,4 @@
     "birthdays": "Add birthdays — you will receive a reminder in time.",
     "recipes": "Create recipes and link them to your meal planner."
   }
-}
+}