fix: backup — Remote-Verzeichnis per mkdir -p vor scp anlegen

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/backup.ts

@@ -98,6 +98,13 @@ async function runBackup(): Promise<void> {
     '-o', 'ConnectTimeout=15',
   ];
 
+  // Zielverzeichnis auf Remote anlegen falls nicht vorhanden
+  await new Promise<void>((resolve, reject) => {
+    const ssh = spawn('ssh', [...sshOpts, sshHost, `mkdir -p ${remotePath}`]);
+    ssh.on('error', reject);
+    ssh.on('close', (code) => code === 0 ? resolve() : reject(new Error(`mkdir -p exit ${code}`)));
+  });
+
   await new Promise<void>((resolve, reject) => {
     const scp = spawn('scp', [...sshOpts, localPath, `${sshHost}:${remotePath}/${filename}`]);
     let scpErr = '';