[Rewrite-Frontend]: Adding new pages for invite link

In the rewrite version of Notangles, currently copying and pasting the friend invite link shows nothing. The idea is developing a new page for inviting friend.

Possible bahaviors:
1. If the user has already logged in, calling the existing `sendFriendRequest` function and show two buttons of "Accept"/"Decline".
2. If the user has not logged in, store the inviting code and guide the user to the login page.
3. If the user is a guest, showing that this functionality can only be accessed with an account.

Start by tracing the rewrite frontend's invite-link entry point, the existing sendFriendRequest function, and the login flow. Done means copied invite links handle logged-in users with Accept/Decline actions, preserve the code for users who must log in, and explain to guests that an account is required.

Written by the indexing model from the issue text.