docs: publish complete product guide and UI fixes

Expand the English README into a practical guide covering installation, accounts, queue controls, automation, history, backups, updates, troubleshooting, and development. Add four sanitized workflow screenshots and enforce their exact public manifest. Restore the animated Backup submenu outside its parent menu, keep expanded account groups naturally sized in the scrolling Accounts list, and strengthen Electron UI regression exit codes.

renderer/i18n.js

@@ -127,6 +127,7 @@
     ['Hoster-Zugangsdaten verwalten und prüfen', 'Manage and verify host account credentials'],
     ['Accounts prüfen', 'Check accounts'],
     ['Account hinzufügen', 'Add account'],
+    ['Noch keine Hoster', 'No hosts yet'],
     ['Füge deinen ersten Hoster-Account hinzu. Die Zugangsdaten werden vor dem Speichern geprüft.', 'Add your first host account. Credentials are verified before saving.'],
     ['Alle ausklappen', 'Expand all'],
     ['Alle einklappen', 'Collapse all'],
@@ -510,7 +511,7 @@
     const textSources = new WeakMap();
     const textRendered = new WeakMap();
     const attributeSources = new WeakMap();
-    const attributes = ['aria-label', 'placeholder', 'title', 'data-tooltip'];
+    const attributes = ['aria-label', 'placeholder', 'title', 'data-tooltip', 'data-empty-label'];
     let language = 'en';
     let observer = null;