web/components: add missing "button" class to main components

web/src/components/misc/FileReceiver.svelte

@@ -40,7 +40,7 @@
 <div class="open-file-container" class:dragged-over={draggedOver}>
     <Meowbalt emotion="question" />
 
-    <button class="open-file-button" on:click={openFile}>
+    <button class="button open-file-button" on:click={openFile}>
         <div class="dashed-stroke">
             <svg width="100%" height="100%" xmlns="http://www.w3.org/2000/svg">
                 <rect width="100%" height="100%" fill="none" rx="24" ry="24" />

web/src/components/misc/UpdateNotification.svelte

@@ -5,7 +5,7 @@
 </script>
 
 <div id="update-notification" role="alert" aria-atomic="true">
-    <button class="update-button" on:click={() => window.location.reload()}>
+    <button class="button update-button" on:click={() => window.location.reload()}>
         <div class="update-icon">
             <IconComet />
         </div>

web/src/components/queue/ProcessingStatus.svelte

@@ -12,6 +12,7 @@
 <button
     id="processing-status"
     on:click={expandAction}
+    class="button"
     class:completed={progress >= 100}
 >
     <svg