feat(backup): plain JSON export/import + clearer error when decrypt fails

main.js

@@ -1750,12 +1750,19 @@ ipcMain.handle('export-backup', async () => {
   const { canceled, filePath } = await dialog.showSaveDialog(mainWindow, {
     title: 'Backup exportieren',
     defaultPath: `multi-hoster-backup-${new Date().toISOString().slice(0, 10)}.mhu`,
-    filters: [{ name: 'Multi-Hoster Backup', extensions: ['mhu'] }]
+    filters: [
+      { name: 'Multi-Hoster Backup (verschlüsselt)', extensions: ['mhu'] },
+      { name: 'Multi-Hoster Backup (Klartext JSON)', extensions: ['json'] }
+    ]
   });
   if (canceled || !filePath) return { ok: false, canceled: true };
   const config = configStore.load();
-  const encrypted = backupCrypto.encrypt(config);
-  fs.writeFileSync(filePath, encrypted);
+  if (filePath.toLowerCase().endsWith('.json')) {
+    fs.writeFileSync(filePath, JSON.stringify(config, null, 2), 'utf-8');
+  } else {
+    const encrypted = backupCrypto.encrypt(config);
+    fs.writeFileSync(filePath, encrypted);
+  }
   return { ok: true, path: filePath };
 });
 
@@ -1767,7 +1774,11 @@ ipcMain.handle('import-backup', async (_event, legacyPassword) => {
   } else {
     const { canceled, filePaths } = await dialog.showOpenDialog(mainWindow, {
       title: 'Backup importieren',
-      filters: [{ name: 'Multi-Hoster Backup', extensions: ['mhu'] }],
+      filters: [
+        { name: 'Multi-Hoster Backup', extensions: ['mhu', 'json'] },
+        { name: 'Verschlüsselt (.mhu)', extensions: ['mhu'] },
+        { name: 'Klartext (.json)', extensions: ['json'] }
+      ],
       properties: ['openFile']
     });
     if (canceled || !filePaths.length) return { ok: false, canceled: true };
@@ -1776,14 +1787,25 @@ ipcMain.handle('import-backup', async (_event, legacyPassword) => {
     _lastImportPath = sourcePath;
   }
   let imported;
-  try {
-    imported = backupCrypto.decrypt(buffer, legacyPassword);
-  } catch (err) {
-    if (err && err.needsPassword) {
-      return { ok: false, needsPassword: true };
+  const looksLikeJson = buffer.length >= 1 && (buffer[0] === 0x7B || buffer[0] === 0x20 || buffer[0] === 0x0A || buffer[0] === 0x0D || buffer[0] === 0x09 || buffer[0] === 0xEF);
+  if (looksLikeJson) {
+    try {
+      const text = buffer.toString('utf-8').replace(/^\uFEFF/, '');
+      imported = JSON.parse(text);
+    } catch (err) {
+      _lastImportPath = null;
+      return { ok: false, error: 'Klartext-Backup ist kein gültiges JSON: ' + (err.message || err) };
+    }
+  } else {
+    try {
+      imported = backupCrypto.decrypt(buffer, legacyPassword);
+    } catch (err) {
+      if (err && err.needsPassword) {
+        return { ok: false, needsPassword: true, hint: 'Falls dieses Backup mit der aktuellen Version erzeugt wurde, ist die Datei vermutlich beim Transfer beschädigt worden (z. B. FTP-Text-Modus). Versuch es mit einem Klartext-JSON-Export.' };
+      }
+      _lastImportPath = null;
+      throw err;
     }
-    _lastImportPath = null;
-    throw err;
   }
   _lastImportPath = null;
   // Validate imported data has required structure

renderer/app.js

@@ -1443,7 +1443,7 @@ async function doBackupExport() {
   }
 }
 
-function askLegacyBackupPassword() {
+function askLegacyBackupPassword(hint) {
   return new Promise((resolve) => {
     const overlay = document.createElement('div');
     overlay.className = 'modal-overlay';
@@ -1456,7 +1456,7 @@ function askLegacyBackupPassword() {
     const header = document.createElement('div');
     header.className = 'modal-header';
     const h3 = document.createElement('h3');
-    h3.textContent = 'Passwort erforderlich';
+    h3.textContent = 'Backup nicht entschlüsselbar';
     header.appendChild(h3);
 
     const body = document.createElement('div');
@@ -1464,7 +1464,15 @@ function askLegacyBackupPassword() {
     const p = document.createElement('p');
     p.style.margin = '0 0 10px';
     p.style.fontSize = '13px';
-    p.textContent = 'Dieses Backup wurde mit einem Passwort verschlüsselt.';
+    p.textContent = 'Wenn das Backup mit der alten Passwort-Option (vor v3.0) erstellt wurde, hier eingeben.';
+    if (hint) {
+      const p2 = document.createElement('p');
+      p2.style.margin = '0 0 10px';
+      p2.style.fontSize = '12px';
+      p2.style.color = 'var(--text-dim)';
+      p2.textContent = hint;
+      body.appendChild(p2);
+    }
     const input = document.createElement('input');
     input.type = 'password';
     input.className = 'key-input';
@@ -1508,7 +1516,7 @@ async function doBackupImport(legacyPassword) {
     const result = await window.api.importBackup(pw);
     if (!result || result.canceled) return;
     if (result.needsPassword) {
-      const entered = await askLegacyBackupPassword();
+      const entered = await askLegacyBackupPassword(result.hint);
       if (entered) doBackupImport(entered);
       return;
     }