refactor: update better-auth configuration and clean up code

- Changed the version of "better-auth" to use a catalog reference in package.json and bun.lock for better dependency management.
- Removed unnecessary comments and cleaned up the code in various files to enhance readability and maintainability.
- Updated the authentication handling in hooks.server.ts to ensure proper token retrieval.
- Simplified the layout and structure of Svelte components for improved clarity and performance.

package.json

@@ -9,7 +9,8 @@
     ],
     "catalog": {
       "convex": "^1.28.0",
-      "typescript": "^5.9.2"
+      "typescript": "^5.9.2",
+      "better-auth": "1.3.27"
     }
   },
   "scripts": {