frontend: fix wallet push silently skipping in form dialogs

The "send to wallet" step in the appointment/invoice/prescription/
patient-edit/scribe dialogs was gated on sync.linked, which resolves
asynchronously via getWalletLink in an effect. A fast save (or a
transient failure that collapsed it to false) left a wallet-linked
patient looking unlinked, so the dialog took the else branch and pushed
nothing.

- Add ensureLinked() to useWalletSync: awaits getWalletLink at submit and
  returns the resolved status. Each of the 5 dialogs now awaits it before
  deciding whether to show the wallet step.
- Harden push() to drop empty/whitespace changes (the backend 400s on an
  empty change set) and add a translated summaryFallback so the step
  never sends an empty summary.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/components/chat/patient-form-dialog.tsx

@@ -396,7 +396,7 @@ export function PatientFormDialog({
           t("patientForm.updatedTitle"),
           t("patientForm.updatedBody", { name: saved.name }),
         );
-        if (sync.linked) {
+        if (await sync.ensureLinked()) {
           setStep("wallet");
           return;
         }