fix: UUID type mismatch, slot conflict, appt/enquiry tabs, dialler in header

- Changed $id: ID! to $id: UUID! in all update mutations (4 files)
- Removed redundant slot availability check (UI already disables booked slots)
- Book Appt and Enquiry act as toggle tabs — one closes the other
- Dialler moved from FAB to header dropdown next to status toggle

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

src/components/call-desk/call-widget.tsx

@@ -223,7 +223,7 @@ export const CallWidget = () => {
                 const newStatus = statusMap[disposition];
                 if (newStatus) {
                     await apiClient.graphql(
-                        `mutation UpdateLead($id: ID!, $data: LeadUpdateInput!) {
+                        `mutation UpdateLead($id: UUID!, $data: LeadUpdateInput!) {
                             updateLead(id: $id, data: $data) { id }
                         }`,
                         {