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/styles.css

@@ -2083,7 +2083,7 @@ select.hs-input { max-width: none; width: auto; min-width: 140px; }
 }
 
 .menu-opening {
-  animation: menu-unfold 180ms cubic-bezier(.2, .8, .2, 1) both;
+  animation: menu-unfold 180ms cubic-bezier(.2, .8, .2, 1);
 }
 
 .menu-closing {
@@ -3201,6 +3201,7 @@ input[type="checkbox"] {
   min-height: 0;
   padding: 12px 16px 16px;
   gap: 8px;
+  grid-auto-rows: max-content;
   overflow: auto;
 }
 
@@ -3244,7 +3245,7 @@ input[type="checkbox"] {
 }
 
 .view-sidebar-hosters:empty::after {
-  content: "Noch keine Hoster";
+  content: attr(data-empty-label);
   color: var(--text-dim);
   font-size: 10px;
 }