Position download button in corner + better Arabic font

- Move export button outside header-actions to enable absolute positioning
- Button now positioned at top-right (LTR) / top-left (RTL)
- Switch from Tajawal to IBM Plex Sans Arabic (slicker, more technical)
- Add RTL-specific font-family in CSS

public/index.html

@@ -17,7 +17,7 @@
     <link rel="manifest" href="%PUBLIC_URL%/manifest.json" />
     <link rel="preconnect" href="https://fonts.googleapis.com">
     <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
-    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600&family=Tajawal:wght@400;500;700&display=swap" rel="stylesheet">
+    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600&family=IBM+Plex+Sans+Arabic:wght@400;500;600;700&display=swap" rel="stylesheet">
     <!--
       Notice the use of %PUBLIC_URL% in the tags above.
       It will be replaced with the URL of the `public` folder during the build.