fix(release): fehlende Versionsnummern + bgUrl-Validierung

Drei Stellen hatten noch '2.0.0' statt '2.0.1': newtab.html About-Sektion,
data.js Export und app.js Backup-Export. FileReader-Upload in settings.js
validiert jetzt bgUrl via isValidBgUrl() (Defense-in-Depth).

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

src/js/app.js

@@ -105,7 +105,7 @@ async function checkBackupReminder() {
     const notesData = (widgetData && Array.isArray(widgetData.notes)) ? widgetData.notes : [];
     const calcHistory = (widgetData && widgetData.calculator) ? widgetData.calculator.history || [] : [];
     const timerPresets = (widgetData && widgetData.timer) ? widgetData.timer.presets || [] : [];
-    const data = { version: '2.0.0', exported: new Date().toISOString(), boards, settings, notes: notesData, calculator: calcHistory, timerPresets };
+    const data = { version: '2.0.1', exported: new Date().toISOString(), boards, settings, notes: notesData, calculator: calcHistory, timerPresets };
     const blob = new Blob([JSON.stringify(data, null, 2)], { type: 'application/json' });
     const url  = URL.createObjectURL(blob);
     const a    = document.createElement('a');

src/js/data.js

@@ -28,7 +28,7 @@ function initDataButtons() {
   btnExport.addEventListener('click', async () => {
     const widgetData = await Store.get('widgetStates');
     const data = {
-      version: '2.0.0',
+      version: '2.0.1',
       exported: new Date().toISOString(),
       boards,
       settings,

src/js/settings.js

@@ -200,6 +200,7 @@ function bindSettingsEvents() {
     if (!file) return;
     const reader = new FileReader();
     reader.onload = async ev => {
+      if (!isValidBgUrl(ev.target.result)) return;
       settings.bgUrl = ev.target.result;
       document.getElementById('bgLayer').style.backgroundImage = `url('${ev.target.result}')`;
       await saveSettings();