feat: reveal available updates beside speed

Collapse the header update action completely when no update exists and animate the green action outward to the left of the fixed bandwidth widget only after a real update is detected.

renderer/index.html

@@ -54,6 +54,12 @@
     </div>
     <div class="header-spacer" aria-hidden="true"></div>
     <div class="header-cluster header-utilities">
+      <div class="header-update-slot" id="headerUpdateSlot" aria-hidden="true">
+        <button class="header-update-button" id="headerUpdateBtn" title="Nach Aktualisierungen suchen" aria-label="Nach Aktualisierungen suchen" data-tooltip="Nach Aktualisierungen suchen" tabindex="-1" disabled>
+          <svg class="header-action-icon" aria-hidden="true"><use href="#icon-download"></use></svg>
+          <span class="header-update-label">Update</span>
+        </button>
+      </div>
       <div class="upload-speed-sparkline" id="uploadSpeedSparkline" title="Aktuelle Upload-Geschwindigkeit" aria-label="Aktuelle Upload-Geschwindigkeit">
         <span class="upload-speed-chart" aria-hidden="true">
           <span class="upload-speed-baseline"></span>
@@ -61,10 +67,6 @@
         </span>
         <strong id="uploadSpeedValue">0 B/s</strong>
       </div>
-      <button class="header-update-button" id="headerUpdateBtn" title="Nach Aktualisierungen suchen" aria-label="Nach Aktualisierungen suchen" data-tooltip="Nach Aktualisierungen suchen">
-        <svg class="header-action-icon" aria-hidden="true"><use href="#icon-download"></use></svg>
-        <span class="header-update-label">Update</span>
-      </button>
       <span class="header-divider" aria-hidden="true"></span>
       <nav class="menu-bar" id="menuBar" aria-label="Anwendungsmenüs">
         <div class="menu-bar-item" data-menu="datei">