Fix: Cancel NIP-46 handshake on login modal cancellation

Implemented a mechanism to cancel the pending NIP-46 handshake when the user clicks 'Cancel' in the login modal.
- Added `pendingHandshakeCancel` callback to `NostrClient` to reject the handshake promise.
- Updated `LoginModalController` to invoke `disconnectRemoteSigner` on cancellation.
- Prevented `onLoginError` callback from triggering when the error code is `login-cancelled`.

Co-authored-by: PR0M3TH3AN <[email protected]>

js/ui/loginModalController.js

@@ -1487,6 +1487,7 @@ export default class LoginModalController {
             this.rejectPendingTask(this.createCancellationError(), {
               type: "add-profile",
             });
+            this.handleProviderDisconnect("nip46");
             cleanup();
           } else {
             finish(null, { keepMounted: false });
@@ -2392,6 +2393,13 @@ export default class LoginModalController {
           return;
         }
 
+        if (
+          rejectionError.code === "login-cancelled" ||
+          rejectionError.code === "user-cancelled"
+        ) {
+          return;
+        }
+
         await safeInvokeAsync(this.callbacks.onLoginError, {
           provider: entry.provider.source || entry.provider,
           error: rejectionError,