fix(clinic-invitation): provision doctor accounts and repair panel actions

The invitation flow never created an account for the invitee. accept() only
looked up an existing doctor by mobile, so for a brand-new invitee it marked
the invitation accepted and burned the token while leaving doctor_id NULL —
no login, no clinic link, and every doctor-facing endpoint 404ing afterwards.

- invite/accept now provision the users + doctors pair, claim the profile on
  accept, link it to the clinic, and SMS generated credentials when the user
  has no password. Existing passwords are never overwritten.
- accept runs in one transaction so an invitation can no longer be marked
  accepted without its doctor profile and clinic link.
- changeStatus accepts `pending`, refreshing the token and re-sending the SMS
  so reactivating a suspended invitation yields a link that actually works.
  Answered invitations are rejected with 409.
- DELETE returns 200 with the standard envelope instead of a bodyless 204,
  which made the admin panel show a false error toast; api.ts also stops
  calling res.json() on empty responses.
- The clinic-doctors settings page sent the active context uuid as the clinic
  uuid, so users holding both a doctor and a clinic context got 404 on every
  invitation action. It now always resolves the clinic context.
- Adds app:invitations:repair to fix invitations already left orphaned.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/admin/lib/api.ts

@@ -71,6 +71,11 @@ async function request<T>(
     );
   }
 
+  // پاسخ بدون بدنه (۲۰۴ یا Content-Length صفر) نباید به res.json() برسد
+  if (res.status === 204 || res.headers.get('Content-Length') === '0') {
+    return null as T;
+  }
+
   return res.json() as Promise<T>;
 }