refactor(state): clean layoutStore, add selectors, centralise STALE constants

- layoutStore: remove 4 dead field groups (pinnedPanels, selectedResultId,
  compareTrayVisible, notificationsOpen) — none were read outside the store
- CompareTray: drop dead useLayoutStore side-effect (state was write-only)
- 8 components: replace bare useStore() with explicit selectors / useShallow
  to prevent unnecessary re-renders on unrelated state mutations
- lib/constants: add STALE_MARKET_SIGNALS + STALE_REVIEW_QUEUE (30s each)
- useMarketSignals, useReviewQueue: use global constants instead of
  hook-local magic numbers
- Add STATE_MANAGEMENT.md: decision tree + rules for RQ/Zustand/local/derived

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

src/components/assistant/GlobalAIAssistantButton.tsx

@@ -3,7 +3,8 @@ import { Sparkles } from 'lucide-react'
 import { useAssistantStore } from '../../stores/assistantStore'
 
 export function GlobalAIAssistantButton() {
-  const { isOpen, open } = useAssistantStore()
+  const isOpen = useAssistantStore(s => s.isOpen)
+  const open = useAssistantStore(s => s.open)
 
   return (
     <Tooltip title="AI Assistent öffnen" placement="left">

src/components/assistant/GlobalAIAssistantDrawer.tsx

@@ -2,6 +2,7 @@ import { useCallback, useEffect, useRef, useState } from 'react'
 import { Box, Divider, Drawer, IconButton, TextField, Tooltip, Typography } from '@mui/material'
 import { RotateCcw, Send, Sparkles, X } from 'lucide-react'
 import { useLocation } from 'react-router'
+import { useShallow } from 'zustand/react/shallow'
 import { useAssistantStore } from '../../stores/assistantStore'
 import { useSessionStore } from '../../stores/sessionStore'
 import { aiAssistantService } from '../../services/aiAssistantService'
@@ -21,7 +22,7 @@ function resolveWorkspace(pathname: string): WorkspaceType | null {
 
 export function GlobalAIAssistantDrawer() {
   const { isOpen, close, context, setContext, messages, isLoading, error, addMessage, setLoading, setError, clearConversation } =
-    useAssistantStore()
+    useAssistantStore(useShallow(s => s))
 
   const { currentUser } = useSessionStore()
   const location = useLocation()

src/components/layout/AppShell.tsx

@@ -17,8 +17,10 @@ import { WorkspaceType } from '../../domain/enums'
 // ---------------------------------------------------------------------------
 
 export function AppShell() {
-  const { activeWorkspace, sidebarCollapsed, setActiveWorkspace, toggleSidebar } =
-    useLayoutStore()
+  const activeWorkspace = useLayoutStore(s => s.activeWorkspace)
+  const sidebarCollapsed = useLayoutStore(s => s.sidebarCollapsed)
+  const setActiveWorkspace = useLayoutStore(s => s.setActiveWorkspace)
+  const toggleSidebar = useLayoutStore(s => s.toggleSidebar)
   const { currentUser } = useSessionStore()
   const navigate = useNavigate()
   const location = useLocation()

src/components/layout/CompareTray.tsx

@@ -1,9 +1,7 @@
-import { useEffect } from 'react'
 import { useNavigate, useLocation } from 'react-router'
 import { Box, Button, IconButton, Typography } from '@mui/material'
 import { X } from 'lucide-react'
 import { useCompareStore } from '../../stores/compareStore'
-import { useLayoutStore } from '../../stores/layoutStore'
 
 const TYPE_DOT: Record<string, string> = {
   VERIFIED_PORTFOLIO:  '#1e3a5f',
@@ -14,15 +12,10 @@ const TYPE_DOT: Record<string, string> = {
 
 export function CompareTray() {
   const { compareItems, removeFromCompare, clearCompare } = useCompareStore()
-  const { setCompareTrayVisible } = useLayoutStore()
   const navigate = useNavigate()
   const location = useLocation()
   const isDemand = location.pathname.startsWith('/demand')
 
-  useEffect(() => {
-    setCompareTrayVisible(compareItems.length > 0 && isDemand)
-  }, [compareItems.length, setCompareTrayVisible, isDemand])
-
   if (!isDemand) return null
 
   const getTitle = (item: (typeof compareItems)[number]) => {

src/components/layout/RightContextPanel.tsx

@@ -18,7 +18,9 @@ const PANEL_PLACEHOLDERS: Record<RightPanelContentType, string> = {
 }
 
 export function RightContextPanel() {
-  const { isRightPanelOpen, rightPanelContentType, closeRightPanel } = useLayoutStore()
+  const isRightPanelOpen = useLayoutStore(s => s.isRightPanelOpen)
+  const rightPanelContentType = useLayoutStore(s => s.rightPanelContentType)
+  const closeRightPanel = useLayoutStore(s => s.closeRightPanel)
 
   const title = rightPanelContentType ? PANEL_TITLES[rightPanelContentType] : ''
   const placeholder = rightPanelContentType ? PANEL_PLACEHOLDERS[rightPanelContentType] : ''

src/components/supply/ReminderFeed.tsx

@@ -1,5 +1,6 @@
 import { Box, Typography } from '@mui/material'
 import { useReminders } from '../../hooks/useReminders'
+import { useShallow } from 'zustand/react/shallow'
 import { useReminderStore } from '../../stores/reminderStore'
 import { ReminderListRow } from './ReminderListRow'
 import { ReminderCard } from './ReminderCard'
@@ -34,7 +35,13 @@ export function ReminderFeed() {
   const {
     filterType, filterStatus, filterPriority, searchQuery, viewMode,
     setFilterType, setFilterStatus, setFilterPriority, setSearchQuery,
-  } = useReminderStore()
+  } = useReminderStore(useShallow(s => ({
+    filterType: s.filterType, filterStatus: s.filterStatus,
+    filterPriority: s.filterPriority, searchQuery: s.searchQuery,
+    viewMode: s.viewMode, setFilterType: s.setFilterType,
+    setFilterStatus: s.setFilterStatus, setFilterPriority: s.setFilterPriority,
+    setSearchQuery: s.setSearchQuery,
+  })))
 
   if (isLoading) return <ReminderSkeleton />
 

src/components/supply/ReminderFilterBar.tsx

@@ -1,5 +1,6 @@
 import { Box, ToggleButtonGroup, ToggleButton, TextField, InputAdornment, Typography } from '@mui/material'
 import { Search } from 'lucide-react'
+import { useShallow } from 'zustand/react/shallow'
 import { useReminderStore } from '../../stores/reminderStore'
 import { ReminderType, ReminderStatus, ReminderPriority } from '../../domain/reminder'
 import type { ReminderType as ReminderTypeType, ReminderStatus as ReminderStatusType, ReminderPriority as ReminderPriorityType } from '../../domain/reminder'
@@ -36,7 +37,13 @@ export function ReminderFilterBar() {
     filterPriority, setFilterPriority,
     searchQuery, setSearchQuery,
     viewMode, setViewMode,
-  } = useReminderStore()
+  } = useReminderStore(useShallow(s => ({
+    filterType: s.filterType, setFilterType: s.setFilterType,
+    filterStatus: s.filterStatus, setFilterStatus: s.setFilterStatus,
+    filterPriority: s.filterPriority, setFilterPriority: s.setFilterPriority,
+    searchQuery: s.searchQuery, setSearchQuery: s.setSearchQuery,
+    viewMode: s.viewMode, setViewMode: s.setViewMode,
+  })))
 
   return (
     <Box className="flex flex-col gap-3">