Refactor fetchNostrContacts

[shubhamkmr04]

• The code now uses Promise.all() to wait for all asynchronous operations to complete before proceeding ensuring proper execution flow.
• Previously setState() was called inside the loop, which could result in multiple state updates and unnecessary re-renders. Now setState() is called only once after all asynchronous operations are completed, reducing unnecessary re-renders and improving performance.

[kaloudis]

tACK