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/campaigns/campaign-edit-slideout.tsx

@@ -53,7 +53,7 @@ export const CampaignEditSlideout = ({ isOpen, onOpenChange, campaign, onSaved }
             const budgetMicros = budget ? Number(budget) * 1_000_000 : null;
 
             await apiClient.graphql(
-                `mutation UpdateCampaign($id: ID!, $data: CampaignUpdateInput!) {
+                `mutation UpdateCampaign($id: UUID!, $data: CampaignUpdateInput!) {
                     updateCampaign(id: $id, data: $data) { id }
                 }`,
                 {