Ticket-System, Web-Composer und Nachrichten-Bearbeitung

- Tickets: /ticket-setup postet 🎫-Button; Klick erstellt privaten Thread
  (ein offenes Ticket pro User), Schließen-Button sperrt + archiviert
- Composer auf der Setup-Seite: Nachricht/Embed als Bot in beliebigen Kanal
  senden oder per Message-ID bearbeiten (nur eigene Bot-Posts)
- API v1: PATCH /api/v1/message — Skripte können ihre Bot-Posts aktualisieren
- Setting ticket_channel_id; README ergänzt

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/db.js

@@ -252,6 +252,26 @@ export function commitHeatmap() {
         .all();
 }
 
+// Ticket-System (Button → privater Thread)
+db.exec(`
+    CREATE TABLE IF NOT EXISTS tickets (
+        thread_id TEXT PRIMARY KEY,
+        user_id   TEXT NOT NULL,
+        status    TEXT NOT NULL DEFAULT 'open',
+        opened_at TEXT NOT NULL DEFAULT (datetime('now'))
+    );
+`);
+const insertTicket = db.prepare('INSERT INTO tickets (thread_id, user_id) VALUES (?, ?)');
+const getTicketStmt = db.prepare('SELECT * FROM tickets WHERE thread_id = ?');
+const closeTicketStmt = db.prepare(`UPDATE tickets SET status = 'closed' WHERE thread_id = ?`);
+const openTicketByUserStmt = db.prepare(
+    `SELECT * FROM tickets WHERE user_id = ? AND status = 'open'`
+);
+export const saveTicket = (threadId, userId) => insertTicket.run(threadId, userId);
+export const getTicket = (threadId) => getTicketStmt.get(threadId) ?? null;
+export const closeTicket = (threadId) => closeTicketStmt.run(threadId);
+export const openTicketOf = (userId) => openTicketByUserStmt.get(userId) ?? null;
+
 // Modmail: DM-Konversationen ↔ Staff-Threads
 db.exec(`
     CREATE TABLE IF NOT EXISTS modmail (