feat: add svelte-sonner dependency and enhance NotificationBell component

- Added `svelte-sonner` to dependencies for improved notification handling.
- Refactored the `NotificationBell.svelte` component for better readability and maintainability, including code formatting and structure improvements.
- Updated `package.json` and `bun.lock` to reflect the new dependency.

package.json

@@ -24,7 +24,8 @@
     "@tanstack/svelte-form": "^1.23.8",
     "chart.js": "^4.5.1",
     "lucide-svelte": "^0.548.0",
-    "svelte-chartjs": "^3.1.5"
+    "svelte-chartjs": "^3.1.5",
+    "svelte-sonner": "^1.0.5"
   },
   "optionalDependencies": {
     "@rollup/rollup-win32-x64-msvc": "^4.52.5"