feat: AI sidebar full height with collapsed icon strip and drag resize

- AISidebar: full height, right of TopBar and Toolbar (all pages except AI Assistant)
- AISidebar: collapsed mode shows narrow 48px icon strip with KI button
- AISidebar: expanded mode uses ResizablePanel with drag-to-resize (240-600px)
- AppShell: moved AISidebar outside inner content container to full-height flex
- uiStore: renamed aiSidebarOpen→aiSidebarCollapsed (default: true=collapsed)
- TopBar: AI button highlights when sidebar is expanded

frontend/src/store/uiStore.ts

@@ -14,14 +14,14 @@ export interface UIState {
   theme: Theme;
   locale: Locale;
   sidebarOpen: boolean;
-  aiSidebarOpen: boolean;
+  aiSidebarCollapsed: boolean;
   toasts: Toast[];
   setTheme: (theme: Theme) => void;
   setLocale: (locale: Locale) => void;
   toggleSidebar: () => void;
   setSidebarOpen: (open: boolean) => void;
   toggleAISidebar: () => void;
-  setAISidebarOpen: (open: boolean) => void;
+  setAISidebarCollapsed: (collapsed: boolean) => void;
   addToast: (toast: Omit<Toast, 'id'>) => void;
   removeToast: (id: string) => void;
   clearToasts: () => void;
@@ -33,7 +33,7 @@ export const useUIStore = create<UIState>((set) => ({
   theme: (localStorage.getItem('leocrm_theme') as Theme) || 'light',
   locale: (localStorage.getItem('leocrm_lang') as Locale) || 'de',
   sidebarOpen: true,
-  aiSidebarOpen: false,
+  aiSidebarCollapsed: true,
   toasts: [],
   setTheme: (theme) => {
     localStorage.setItem('leocrm_theme', theme);
@@ -45,8 +45,8 @@ export const useUIStore = create<UIState>((set) => ({
   },
   toggleSidebar: () => set((s) => ({ sidebarOpen: !s.sidebarOpen })),
   setSidebarOpen: (open) => set({ sidebarOpen: open }),
-  toggleAISidebar: () => set((s) => ({ aiSidebarOpen: !s.aiSidebarOpen })),
-  setAISidebarOpen: (open) => set({ aiSidebarOpen: open }),
+  toggleAISidebar: () => set((s) => ({ aiSidebarCollapsed: !s.aiSidebarCollapsed })),
+  setAISidebarCollapsed: (collapsed) => set({ aiSidebarCollapsed: collapsed }),
   addToast: (toast) => {
     const id = `toast-${++toastIdCounter}`;
     set((s) => ({ toasts: [...s.toasts, { ...toast, id }] }));