Version 1.7.3: Fehlende Menü-Icons ergänzt

- MainWindow: Icons für drei bislang icon-lose Menü-Aktionen gesetzt
  - "Alle XML-Dateien transformieren" → play-circle
  - "Aus Datenbank laden" → database (neu)
  - "Worker-Pool-Metriken" → activity (neu)
- Zwei neue Feather-Icons (database, activity) ergänzt: Download-Skript,
  resources.qrc und resources_rc.py (via pyside6-rcc) aktualisiert

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/res/icons/activity.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><polyline points="22 12 18 12 15 21 9 3 6 12 2 12"/></svg>

src/res/icons/database.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><ellipse cx="12" cy="5" rx="9" ry="3"/><path d="M21 12c0 1.66-4 3-9 3s-9-1.34-9-3"/><path d="M3 5v14c0 1.66 4 3 9 3s9-1.34 9-3V5"/></svg>

src/res/resources.qrc

@@ -21,5 +21,7 @@
         <file>icons/file-plus.svg</file>
         <file>icons/columns.svg</file>
         <file>icons/sliders.svg</file>
+        <file>icons/database.svg</file>
+        <file>icons/activity.svg</file>
     </qresource>
 </RCC>