feat: window management system with minimize, fullscreen, and AI chat split

- Window manager store (Zustand) for managing open/minimized/fullscreen windows
- Window component with header controls: KI-Chat toggle, fullscreen, minimize, close
- AI chat panel with streaming chat via existing /ai/sessions API
- WindowContainer renders all non-minimized windows
- TopBar shows minimized windows as clickable pills
- ContactEditForm extracted from ContactEditModal for window rendering
- ContactsList and ContactDetailPage use openWindow() instead of modal state
- Draggable windows with z-index management

frontend/src/pages/ContactsList.tsx

@@ -15,7 +15,8 @@ import { usePluginToolbarStore } from '@/store/pluginToolbarStore';
 import { ContactFolderTree, type ContactFilter } from '@/components/contacts/ContactFolderTree';
 import { ContactList, type ContactViewMode } from '@/components/contacts/ContactList';
 import { ContactDetail } from '@/components/contacts/ContactDetail';
-import { ContactEditModal } from '@/components/contacts/ContactEditModal';
+import { ContactEditForm } from '@/components/contacts/ContactEditForm';
+import { useWindowStore } from '@/store/windowStore';
 import { SavedFilters } from '@/components/SavedFilters';
 import { ArrowDownAZ, ArrowUpZA, ChevronLeft, LayoutGrid, List, Plus } from 'lucide-react';
 import {
@@ -39,8 +40,7 @@ export function ContactsListPage() {
   const [viewMode, setViewMode] = useState<ContactViewMode>('list');
   const [selectedContactId, setSelectedContactId] = useState<string | null>(null);
   const [activeView, setActiveView] = useState<'folders' | 'list' | 'detail'>('folders');
-  const [editModalOpen, setEditModalOpen] = useState(false);
-  const [editingContact, setEditingContact] = useState<UnifiedContact | null>(null);
+  const openWindow = useWindowStore((s) => s.openWindow);
 
   // Debounce search
   useEffect(() => {
@@ -134,19 +134,40 @@ export function ContactsListPage() {
     setPage(1);
   }, []);
 
+  // Handle edit modal saved
+  const handleSaved = useCallback((id: string) => {
+    setSelectedContactId(id);
+    setActiveView('detail');
+  }, []);
+
   // Handle create
   const handleCreate = useCallback(() => {
-    setEditingContact(null);
-    setEditModalOpen(true);
-  }, []);
+    openWindow({
+      title: t('contacts.create'),
+      type: 'contact-create',
+      component: ContactEditForm,
+      componentProps: {
+        onClose: () => {},
+        onSaved: handleSaved,
+      },
+    });
+  }, [openWindow, t, handleSaved]);
 
   // Handle edit
   const handleEdit = useCallback(() => {
     if (selectedContact) {
-      setEditingContact(selectedContact);
-      setEditModalOpen(true);
+      openWindow({
+        title: t('contacts.edit'),
+        type: 'contact-edit',
+        component: ContactEditForm,
+        componentProps: {
+          contact: selectedContact,
+          onClose: () => {},
+          onSaved: handleSaved,
+        },
+      });
     }
-  }, [selectedContact]);
+  }, [selectedContact, openWindow, t, handleSaved]);
 
   // Handle delete (from detail)
   const handleDeleted = useCallback(() => {
@@ -154,12 +175,6 @@ export function ContactsListPage() {
     setActiveView('list');
   }, []);
 
-  // Handle edit modal saved
-  const handleSaved = useCallback((id: string) => {
-    setSelectedContactId(id);
-    setActiveView('detail');
-  }, []);
-
   // Register toolbar items
   const registerItems = usePluginToolbarStore((s) => s.registerItems);
   const unregisterPlugin = usePluginToolbarStore((s) => s.unregisterPlugin);
@@ -458,13 +473,7 @@ export function ContactsListPage() {
         )}
       </div>
 
-      {/* Edit/Create Modal */}
-      <ContactEditModal
-        open={editModalOpen}
-        onClose={() => setEditModalOpen(false)}
-        contact={editingContact}
-        onSaved={handleSaved}
-      />
     </div>
   );
 }
+