feat(release): Version auf v2.1.0 bumpen — Calculator Upgrade

Alle 3 Manifests, newtab.html, data.js, app.js auf 2.1.0.
CHANGELOG-Eintrag mit allen 6 neuen Calculator-Modi.

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

src/js/data.js

@@ -28,7 +28,7 @@ function initDataButtons() {
   btnExport.addEventListener('click', async () => {
     const widgetData = await Store.get('widgetStates');
     const data = {
-      version: '2.0.1',
+      version: '2.1.0',
       exported: new Date().toISOString(),
       boards,
       settings,