fix: resolve UI bugs and pasting behavior

- Add global Cmd+V keyboard paste support for downloading links
- Restore striped background styling for alternate rows in download list
- Add ghost rows to seamlessly fill empty download space
- Map correctly formatted item size into the queue immediately
- Remove unused Tauri manager imports from backend

src/App.tsx

@@ -155,6 +155,25 @@ function App() {
     initNotifications();
   }, []);
 
+  useEffect(() => {
+    const handlePaste = (e: ClipboardEvent) => {
+      if (
+        e.target instanceof HTMLInputElement ||
+        e.target instanceof HTMLTextAreaElement ||
+        e.target instanceof HTMLSelectElement ||
+        (e.target as HTMLElement).isContentEditable
+      ) {
+        return;
+      }
+      const text = e.clipboardData?.getData('text/plain');
+      if (text && text.trim().length > 0) {
+        useDownloadStore.getState().openAddModalWithUrls(text.trim());
+      }
+    };
+    window.addEventListener('paste', handlePaste);
+    return () => window.removeEventListener('paste', handlePaste);
+  }, []);
+
   useEffect(() => {
     const root = window.document.documentElement;