feat(tickets): add tickets API client, update integrations API for paginated search, fix callers

- Create frontend/src/api/tickets.ts with ticketsApi (resources, status, create, ai-parse, priorities, search)
- Update integrationsApi.searchTickets and searchTicketsQueue return types from PSATicketSearchResult[] to TicketListResponse
- Fix TicketQueue.tsx to use results.items (append/set) and results.items.length for pagination check
- Fix TicketPickerModal.tsx to use results.items when setting search results
- Export ticketsApi from api/index.ts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/session/TicketPickerModal.tsx

@@ -56,7 +56,7 @@ export function TicketPickerModal({ open, onClose, sessionId, onLinked, onSelect
         query: query.trim(),
         include_closed: closed,
       })
-      setSearchResults(results)
+      setSearchResults(results.items)
       setHasSearched(true)
     } catch (err: unknown) {
       const message =