feat: consolidate AI settings into one page with tabs

- New SettingsAI page with 3 tabs: KI Assistent, Proaktive KI, MCP
- Remove individual AI/proactive/mcp from settings nav
- Settings nav now 6 items: Stammdaten, Nutzerverwaltung, System, Mail, KI Einstellungen, Benachrichtigungen

frontend/src/pages/Settings.tsx

@@ -19,10 +19,8 @@ export function SettingsPage() {
     { to: '/settings/user-management', label: 'Nutzerverwaltung', icon: '\ud83d\udc65' },
     { to: '/settings/system', label: 'System', icon: '\u2699\ufe0f' },
     { to: '/settings/mail', label: t('mail.settings'), icon: '\ud83d\udce7' },
-    { to: '/settings/ai', label: t('nav.aiAssistant'), icon: '\ud83e\udde0' },
-    { to: '/settings/ai-proactive', label: 'Proaktive KI', icon: '\ud83e\udd16' },
+    { to: '/settings/ai-settings', label: 'KI Einstellungen', icon: '\ud83e\udde0' },
     { to: '/settings/notifications', label: t('settings.notifications'), icon: '\ud83d\udd14' },
-    { to: '/settings/mcp', label: t('settings.mcp', 'MCP'), icon: '\ud83d\udd27' },
   ];
 
   const existingPaths = new Set(hardcodedNavItems.map(item => item.to));

frontend/src/pages/SettingsAI.tsx

@@ -0,0 +1,46 @@
+import React, { useState } from 'react';
+import { useTranslation } from 'react-i18next';
+import { AISettingsPage } from './AISettings';
+import { ProactiveAISettings } from './ProactiveAISettings';
+import { SettingsMcpPage } from './SettingsMcp';
+
+export function SettingsAIPage() {
+  const { t } = useTranslation();
+  const [activeTab, setActiveTab] = useState<'assistant' | 'proactive' | 'mcp'>('assistant');
+
+  const tabs = [
+    { key: 'assistant' as const, label: t('nav.aiAssistant', 'KI Assistent') },
+    { key: 'proactive' as const, label: t('settings.aiProactive', 'Proaktive KI') },
+    { key: 'mcp' as const, label: t('settings.mcp', 'MCP') },
+  ];
+
+  return (
+    <div data-testid="settings-ai-page">
+      <h1 className="text-2xl font-bold text-secondary-900 mb-6">{t('settings.aiTitle', 'KI Einstellungen')}</h1>
+      <div className="border-b border-secondary-200 mb-6">
+        <nav className="flex gap-1" role="tablist">
+          {tabs.map((tab) => (
+            <button
+              key={tab.key}
+              onClick={() => setActiveTab(tab.key)}
+              className={`px-4 py-2 text-sm font-medium border-b-2 transition-colors ${
+                activeTab === tab.key
+                  ? 'border-primary-600 text-primary-600'
+                  : 'border-transparent text-secondary-500 hover:text-secondary-700 hover:border-secondary-300'
+              }`}
+              role="tab"
+              aria-selected={activeTab === tab.key}
+            >
+              {tab.label}
+            </button>
+          ))}
+        </nav>
+      </div>
+      <div className="mt-4">
+        {activeTab === 'assistant' && <AISettingsPage />}
+        {activeTab === 'proactive' && <ProactiveAISettings />}
+        {activeTab === 'mcp' && <SettingsMcpPage />}
+      </div>
+    </div>
+  );
+}

frontend/src/routes/index.tsx

@@ -36,6 +36,7 @@ const AISettingsPage = React.lazy(() => import('@/pages/AISettings').then(m => (
 const ProactiveAISettings = React.lazy(() => import('@/pages/ProactiveAISettings').then(m => ({ default: m.ProactiveAISettings })));
 const SettingsThemePage = React.lazy(() => import('@/pages/SettingsTheme').then(m => ({ default: m.SettingsThemePage })));
 const SettingsMcpPage = React.lazy(() => import('@/pages/SettingsMcp').then(m => ({ default: m.SettingsMcpPage })));
+const SettingsAIPage = React.lazy(() => import('@/pages/SettingsAI').then(m => ({ default: m.SettingsAIPage })));
 const SettingsMenuOrderPage = React.lazy(() => import('@/pages/SettingsMenuOrder').then(m => ({ default: m.SettingsMenuOrderPage })));
 const SettingsStammdatenPage = React.lazy(() => import('@/pages/SettingsStammdaten').then(m => ({ default: m.SettingsStammdatenPage })));
 const SettingsUserManagementPage = React.lazy(() => import('@/pages/SettingsUserManagement').then(m => ({ default: m.SettingsUserManagementPage })));
@@ -118,6 +119,7 @@ const router = createBrowserRouter([
           { path: 'theme', element: withSuspense(<SettingsThemePage />) },
           { path: 'automation', element: withSuspense(<AutomationSettingsPage />) },
           { path: 'mcp', element: withSuspense(<SettingsMcpPage />) },
+          { path: 'ai-settings', element: withSuspense(<SettingsAIPage />) },
           { path: 'menu', element: withSuspense(<SettingsMenuOrderPage />) },
           { path: '*', element: <PluginRouteRenderer /> },
         ],