refactor: move PipelineItems from Zustand to Provider→Service→React Query

PipelineItems are domain data and must not live in Zustand. Moves the
full stack to the correct layer: MockupPipelineProvider (localStorage
persistence + seed fallback) → pipelineService → usePipeline hooks
(useQuery for reads, useMutation for writes with cache invalidation).

pipelineStore is now UI-only: dialogOpen, pendingItem, openSavedDialog,
closeSavedDialog. All consumers updated to use the new hooks.

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

src/pages/demand/Pipeline.tsx

@@ -8,7 +8,7 @@ import {
 } from '@dnd-kit/core'
 import type { DragEndEvent, DragStartEvent } from '@dnd-kit/core'
 import { TrendingUp } from 'lucide-react'
-import { usePipelineStore } from '../../stores/pipelineStore'
+import { usePipelineItems, useMoveStage } from '../../hooks/usePipeline'
 import { AddToPipelineDialog } from '../../components/shortlist'
 import type { PipelineItem, PipelineStage } from '../../domain/pipeline'
 import { STAGES } from '../../components/pipeline/pipelineConstants'
@@ -20,7 +20,8 @@ import { DetailPanel } from '../../components/pipeline/PipelineDetailPanel'
 
 export default function Pipeline() {
   const navigate = useNavigate()
-  const { items, moveStage } = usePipelineStore()
+  const { data: items = [] } = usePipelineItems()
+  const { mutate: moveStage } = useMoveStage()
   const [selectedItem, setSelectedItem] = useState<PipelineItem | null>(null)
   const [activeId, setActiveId] = useState<string | null>(null)
   const [overId, setOverId] = useState<string | null>(null)
@@ -53,7 +54,7 @@ export default function Pipeline() {
     const targetStage = over.id as PipelineStage
     const item = items.find(i => i.id === active.id)
     if (item && item.stage !== targetStage) {
-      moveStage(item.id, targetStage)
+      moveStage({ id: item.id, stage: targetStage })
     }
   }