adds shadcn, removes skeleton, implements button after styleguide

src/lib/components/ZipDropzone.svelte

@@ -62,7 +62,7 @@
 
 <button
         type="button"
-        class="flex min-h-[calc(-180px+100vh)] w-full grow cursor-pointer flex-col justify-center border-0 bg-transparent p-0 text-center text-inherit appearance-none focus:outline-none transition-colors rounded-2xl {isDragging ? 'bg-gray-100 border-2 border-dashed border-primary-500' : ''} {className}"
+        class="flex min-h-[calc(-180px+100vh)] w-full grow cursor-pointer flex-col justify-center border-0 text-primary bg-transparent p-0 text-center appearance-none focus:outline-none transition-colors rounded-2xl {isDragging ? 'bg-gray-100 border-2 border-dashed border-primary-500' : ''} {className}"
         aria-label="ZIP-Dateien hinzufügen"
         onclick={openFileDialog}
         ondragover={handleDragOver}
@@ -70,8 +70,7 @@
         ondrop={handleDrop}
 >
     <div class="flex flex-row items-baseline justify-center gap-2">
-        <!-- Changed h1 to span for better semantic HTML inside a button -->
-        <span class="text-[20px] font-bold text-primary-900">Dateien hinzufügen</span>
-        <span class="text-[20px] font-extrabold text-primary-900">+</span>
+        <span class="text-[20px] font-bold">Dateien hinzufügen</span>
+        <span class="text-[20px] font-extrabold">+</span>
     </div>
 </button>