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.

packages/backend/package.json

@@ -22,7 +22,7 @@
   "dependencies": {
     "@convex-dev/better-auth": "^0.9.7",
     "@dicebear/avataaars": "^9.2.4",
-    "better-auth": "1.3.27",
+    "better-auth": "catalog:",
     "convex": "catalog:",
     "nodemailer": "^7.0.10"
   }