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/lib/types.ts

@@ -148,13 +148,16 @@ export const RECURRENCE_LABELS: Record<Exclude<Recurrence, ''>, string> = {
   yearly: 'jährlich',
 };
 
+// Set while the last change came from an AI agent via MCP and the user has not touched the entry since
+export type AgentMark = 'created' | 'edited';
+
 export interface Thought {
   id: string;
   userId: string;
   content: string;
   tags: string[];
   priority: PriorityLevel;
-  source: 'manual' | 'voice' | 'webhook';
+  source: 'manual' | 'voice' | 'webhook' | 'agent';
   status: ThoughtStatus;
   isCompleted: boolean;
   convertedType?: 'task' | 'document' | 'list_item' | 'document_block';
@@ -173,6 +176,7 @@ export interface Thought {
   sortOrder?: number;
   createdAt: string;
   triagedAt?: string;
+  agentMark?: AgentMark;
 }
 
 export interface KanbanColumn {
@@ -538,6 +542,7 @@ export interface ListItem {
   sortOrder: number;
   createdAt: string;
   completedAt?: string;
+  agentMark?: AgentMark;
 }
 
 export interface ListShare {