feat: add delete-after-action dialogs and auto-refresh in inbox

- Show confirmation dialog to delete document after download or email send
- Auto-refresh inbox list every 30 seconds
- Rename "Vorschau" button to "Weiterverarbeiten"

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

paperless-frontend/src/pages/InboxPage.tsx

@@ -209,6 +209,11 @@ export default function InboxPage() {
     load();
   }, [load]);
 
+  useEffect(() => {
+    const id = setInterval(load, 30_000);
+    return () => clearInterval(id);
+  }, [load]);
+
   const handleRescan = async () => {
     setRescanning(true);
     const hide = message.loading('Rescan läuft – das kann je nach Anzahl der Dokumente dauern …', 0);
@@ -324,7 +329,7 @@ export default function InboxPage() {
               icon={<EyeOutlined />}
               onClick={() => navigate(`/inbox/${encodeURIComponent(record.id)}`)}
             >
-              Vorschau
+              Weiterverarbeiten
             </Button>
           </Tooltip>
           <Popconfirm