Bump svelte from 5.1.12 to 5.1.15 in /www

Bumps [svelte](https://github.com/sveltejs/svelte/tree/HEAD/packages/svelte) from 5.1.12 to 5.1.15.
- [Release notes](https://github.com/sveltejs/svelte/releases)
- [Changelog](https://github.com/sveltejs/svelte/blob/main/packages/svelte/CHANGELOG.md)
- [Commits](https://github.com/sveltejs/svelte/commits/svelte@5.1.15/packages/svelte)

---
updated-dependencies:
- dependency-name: svelte
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

www/package.json

@@ -10,7 +10,7 @@
   },
   "devDependencies": {
     "@sveltejs/vite-plugin-svelte": "^4.0.0",
-    "svelte": "^5.1.12",
+    "svelte": "^5.1.15",
     "vite": "^5.4.10"
   }
 }