bug: invite form stays stuck when referral invite request fails

[absalonCRC]

Summary

The Invite Friends form sets sending before posting to /api/referrals, then assumes both the request and res.json() succeed. If the network request rejects or the server returns a non-JSON error body, the handler throws before resetting sending, leaving the button stuck in "Sending..." and no useful error message shown.

Steps to reproduce

1. Open /dashboard/referrals.
2. Enter an email address.
3. Make POST /api/referrals fail at the network layer, or return an invalid/non-JSON error response.
4. Click Send Invites.

Expected

The page should recover, re-enable the Send Invites button, and show a clear error.

Actual

The unhandled failure path can leave the form stuck in the loading state.

Proposed fix

Wrap the invite POST flow in try/catch/finally, tolerate non-JSON error responses, and always reset sending.

[morganschp]

Submitted PR #214 for this bug: #214

The fix wraps the invite send flow in try/catch/finally, tolerates non-JSON error responses, always resets the button state, and adds component regression coverage for the failure paths.