feat: implement account switcher component and state management

- Add AccountSwitcher component for managing user accounts with UI for switching, adding, and logging out.
- Create account state manager to handle snapshots of account-specific states for efficient switching.
- Introduce utility functions for account management, including ID generation and avatar color assignment.
- Implement Zustand store for account management, supporting addition, removal, and state retrieval of accounts.

app/[locale]/auth/callback/page.tsx

@@ -53,6 +53,7 @@ function OAuthCallbackInner() {
           sessionStorage.removeItem("oauth_state");
           sessionStorage.removeItem("oauth_code_verifier");
           sessionStorage.removeItem("oauth_server_url");
+          sessionStorage.removeItem("oauth_add_account_mode");
           let redirectTo = `/${params.locale}`;
           try {
             const saved = sessionStorage.getItem('redirect_after_login');