feat: F025 button & action logic audit — global toast, confirm dialog, wired mutations

- Add ToastProvider (global MUI Snackbar stack) + toastStore (Zustand)
- Add ConfirmDialog reusable component for destructive actions
- Wire toast feedback to all async mutations: review status, AI output status,
  match approval, shortlist add/remove/title/finalize, signal review actions
- Fix dead UserMenu buttons (Profil, Einstellungen) — show info toast
- Migrate local Snackbar instances in AddToShortlistDialog and
  FutureSignalDetailPanel to global toast store

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

src/components/layout/UserMenu.tsx

@@ -3,6 +3,7 @@ import { useNavigate } from 'react-router'
 import { Avatar, Box, Divider, IconButton, ListItemIcon, Menu, MenuItem, Typography } from '@mui/material'
 import { LogOut, Settings, User } from 'lucide-react'
 import { useSessionStore } from '../../stores/sessionStore'
+import { useToastStore } from '../../stores/toastStore'
 import { DemoRoleSwitcher } from '../auth/DemoRoleSwitcher'
 
 const ROLE_LABELS: Record<string, string> = {
@@ -27,6 +28,7 @@ export function UserMenu() {
   const [anchorEl, setAnchorEl] = useState<null | HTMLElement>(null)
   const { currentUser, logout } = useSessionStore()
   const navigate = useNavigate()
+  const showToast = useToastStore((s) => s.showToast)
 
   function handleOpen(e: React.MouseEvent<HTMLElement>) {
     setAnchorEl(e.currentTarget)
@@ -75,11 +77,11 @@ export function UserMenu() {
 
         <Divider />
 
-        <MenuItem onClick={handleClose}>
+        <MenuItem onClick={() => { handleClose(); showToast('Profilseite ist in Kürze verfügbar.', 'info') }}>
           <ListItemIcon><User size={16} /></ListItemIcon>
           Profil
         </MenuItem>
-        <MenuItem onClick={handleClose}>
+        <MenuItem onClick={() => { handleClose(); showToast('Einstellungen sind in Kürze verfügbar.', 'info') }}>
           <ListItemIcon><Settings size={16} /></ListItemIcon>
           Einstellungen
         </MenuItem>