ALL-1875 PR-4: Duplicate candidates list UI + ContactsPage tab

## ALL-1875: Contact merge UI + auto duplicate detection — PR 4 of 5 ### Goal Build the Duplicate Candidates list view in the dashboard — a new tab or sub-page under /ws/[id]/contacts showing detected candidate pairs. ### Context - Linear issue: ALL-1875 - Branch: `wilbo/all-1875-duplicate-candidates-ui` - Worktree: `mono-all-1875-duplicate-candidates-ui` - Depends on: PR-3 merged (GraphQL query `duplicateContactCandidates` available) - App: `apps/dashboard` - Route structure: `app/(shell)/ws/[id]/contacts/` ### What to build 1. **New route**: `apps/dashboard/app/(shell)/ws/[id]/contacts/duplicates/page.tsx` - Wraps `<DuplicateCandidatesPage />` 2. **Page component**: `apps/dashboard/components/pages/DuplicateCandidatesPage.tsx` - Query `duplicateContactCandidates(workspaceId, first: 50, orderBy: confidence_desc)` - Card-per-pair layout: two contact name+email+phone chips side by side - Match signals shown as badges (EMAIL MATCH, PHONE MATCH, etc.) - Confidence score badge (e.g. "High" for >=0.8, "Medium" 0.5–0.8) - Actions per row: "Review & Merge" (navigates to merge comparison UI, PR-5) + "Not Duplicates" (calls `dismissContactDuplicate`) - Filter: confidence (all / high / medium) + sort (confidence / date detected) - Empty state when no candidates - Loading skeleton 3. **Navigation entry**: Add "Duplicates" tab or link inside the contacts section nav (look at how contacts page handles tabs, follow the same pattern) 4. **Hook**: `apps/dashboard/hooks/useDuplicateCandidates.ts` - Wraps the GraphQL query with pagination and filter state 5. **Codegen**: Run `yarn codegen` on the dashboard to get typed GQL ops for `duplicateContactCandidates` and `dismissContactDuplicate`. ### Key existing files - `apps/dashboard/components/pages/ContactsPage.tsx` — contacts list reference pattern - `apps/dashboard/components/pages/ContactDetailPage.tsx` — contact card/detail patterns, edges component imports - `apps/dashboard/app/(shell)/ws/[id]/contacts/page.tsx` — route wiring pattern - `apps/dashboard/hooks/useContacts.ts` — hook pattern for contacts query - `apps/dashboard/lib/@generated/graphql.ts` — regenerated by codegen ### Acceptance test - Navigating to /ws/[id]/contacts/duplicates shows candidate pairs - Clicking "Not Duplicates" dismisses the pair (row disappears or shows dismissed state) - Clicking "Review & Merge" navigates to /ws/[id]/contacts/[id]/merge/[otherId] (stub route ok if PR-5 not done) - Empty state shown when no candidates exist - TypeScript type-checks cleanly ### Depends on - PR-3 merged (fleet-task e53c7925-185a-486b-a817-827d49985451) ### Out of scope - The merge comparison/execution UI (PR-5) - Merge history on ContactDetailPage (that's in PR-5)