feat(mcp): delete tasks, create task lists and lists, agent badge; export/import settings category

New MCP tools delete_task (tasks:write), create_task_list (tasks:write) and create_list
(lists:write); list_task_lists now returns the board columns so agents know the valid
kanbanStatus values. Task deletion is a shared helper (deleteTask) for REST and MCP.

Tasks and list items get agent_mark (migration 12): "created" when an agent adds them via MCP,
"edited" when an agent changes them; a change by the user clears it. The new AgentBadge shows
"KI" / "KI geändert" in task rows, Kanban cards, the task detail, the inbox and lists.

Settings: export and import move out of "Webhooks, KI-Agenten & Export" into their own
category "Export & Import". Docs, help, README and changelog updated; v0.29.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/settings/UserSettingsView.tsx

@@ -17,6 +17,7 @@ import {
   Upload,
   Pencil,
   Copy,
+  Archive,
 } from 'lucide-react';
 import { AuthStatus, NotificationEvents, NotificationSettings, PushDevice, User, UserTheme } from '../../lib/types';
 import { ApiKeysPanel } from './ApiKeysPanel';
@@ -65,7 +66,7 @@ interface UserSettingsViewProps {
   onBack: () => void;
 }
 
-type UserSettingsSection = 'profile' | 'appearance' | 'alarms' | 'webhooks';
+type UserSettingsSection = 'profile' | 'appearance' | 'alarms' | 'webhooks' | 'data';
 
 export function buildNotificationSettings(user: User): NotificationSettings {
   const hasLegacy = Array.isArray(user.alarmChannels);
@@ -582,7 +583,7 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
           <div>
             <h1 className="text-base font-bold text-main tracking-tight">Kontoeinstellungen</h1>
             <p className="text-xs text-muted">
-              Persönliches Profil, Design-Themes, Aufgaben-Alarme, Webhooks, KI-Agenten & Daten-Backup
+              Persönliches Profil, Design-Themes, Aufgaben-Alarme, Webhooks, KI-Agenten, Export & Import
             </p>
           </div>
         </div>
@@ -651,8 +652,23 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
           >
             <Key className="w-4 h-4 text-accent flex-shrink-0" />
             <div>
-              <p className="font-semibold">Webhooks, KI-Agenten & Export</p>
-              <p className="text-[10px] text-faint">API-Keys, MCP, Curl & JSON-Backup</p>
+              <p className="font-semibold">Webhooks & KI-Agenten</p>
+              <p className="text-[10px] text-faint">API-Keys, MCP & Curl</p>
+            </div>
+          </button>
+
+          <button
+            onClick={() => setSection('data')}
+            className={`w-full px-3.5 py-3 text-left text-xs font-medium flex items-center gap-2.5 transition-colors ${
+              section === 'data'
+                ? 'bg-panel-elevated text-main border-l-2 border-l-accent'
+                : 'text-muted hover:text-main hover:bg-panel-hover'
+            }`}
+          >
+            <Archive className="w-4 h-4 text-accent flex-shrink-0" />
+            <div>
+              <p className="font-semibold">Export & Import</p>
+              <p className="text-[10px] text-faint">Backups, Obsidian & Wiederherstellen</p>
             </div>
           </button>
         </aside>
@@ -1849,14 +1865,12 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
           )}
 
           {/* ================================================================= */}
-          {/* SECTION 4: PRIVATE WEBHOOKS & EXPORT */}
+          {/* SECTION 4: PRIVATE WEBHOOKS & AI AGENTS */}
           {/* ================================================================= */}
           {section === 'webhooks' && (
             <div className="space-y-5">
               <div className="border-b border-border pb-3">
-                <h2 className="text-sm font-bold text-main">
-                  Webhooks, KI-Agenten & Daten-Export
-                </h2>
+                <h2 className="text-sm font-bold text-main">Webhooks & KI-Agenten</h2>
                 <p className="text-muted mt-0.5">
                   Erstelle persönliche API-Schlüssel, um aus Skripten, Smarthome oder Bots Aufgaben und Gedanken
                   einzuspeisen oder KI-Agenten wie Claude Code und Codex an deine Aufgaben und Listen zu lassen.
@@ -1864,11 +1878,24 @@ export const UserSettingsView: React.FC<UserSettingsViewProps> = ({
               </div>
 
               <ApiKeysPanel />
+            </div>
+          )}
 
-              <div className="pt-4 border-t border-border">
-                <ServerBackupsCard />
+          {/* ================================================================= */}
+          {/* SECTION 5: EXPORT & IMPORT */}
+          {/* ================================================================= */}
+          {section === 'data' && (
+            <div className="space-y-5">
+              <div className="border-b border-border pb-3">
+                <h2 className="text-sm font-bold text-main">Export & Import</h2>
+                <p className="text-muted mt-0.5">
+                  Lade deine Daten als Backup oder Markdown-Archiv herunter, spiele Server-Backups zurück oder importiere
+                  MindSift-Daten und Obsidian-Vaults.
+                </p>
               </div>
 
+              <ServerBackupsCard />
+
               {/* Full Data Backup */}
               <div className="pt-4 border-t border-border flex flex-col sm:flex-row sm:items-center justify-between gap-3">
                 <div>