fix: stop auto-creating Unknown leads on every call

Caller resolver now returns empty IDs for unrecognized numbers instead
of eagerly creating lead+patient records. Records are created when the
agent explicitly books an appointment or logs an enquiry — per PRD.

- caller-resolution.service.ts: return unresolved result, don't create
- call-desk.tsx: toast changed to 'No existing records found'
- appointment-form.tsx: create patient on save if none exists

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/pages/call-desk.tsx

@@ -91,7 +91,7 @@ export const CallDeskPage = () => {
             .then((result) => {
                 setResolvedCaller(result);
                 if (result.isNew) {
-                    notify.info('New Caller', 'Lead and patient records created');
+                    notify.info('New Caller', 'No existing records found for this number');
                 }
             })
             .catch((err) => {