refactor: remove unused authentication files and dependencies; update package.json to streamline dependencies and improve project structure

apps/web/src/lib/auth.ts

@@ -1,7 +0,0 @@
-import { createAuthClient } from "better-auth/client";
-import { convexClient } from "@convex-dev/better-auth/client/plugins";
-
-export const authClient = createAuthClient({
-  baseURL: "http://localhost:5173",
-  plugins: [convexClient()],
-});