feat(kba-drafter): add ability to reset reviewed KBAs back to draft

- Add "Zurück zu Entwurf" button for reviewed status KBAs
- Add handleUnreview() handler to update status from "reviewed" to "draft"
- Import ArrowUndo24Regular icon for the unreview action
- Allow users to continue editing KBAs after review without deletion

This enables editing of reviewed KBAs that need changes before publishing.

Author: SubSonic731

frontend/src/features/kba-drafter/KBADrafterPage.jsx

@@ -54,6 +54,7 @@ import {
   Tag20Regular,
   Search20Regular,
   DocumentSearch20Regular,
+  ArrowUndo24Regular,
 } from "@fluentui/react-icons";
 import * as api from "../../services/api";
 import EditableList from "./components/EditableList";
@@ -456,6 +457,27 @@ export default function KBADrafterPage() {
     }
   };
 
+  // Handler: Unreview (back to draft)
+  const handleUnreview = async () => {
+    if (!currentDraft) return;
+
+    setSaving(true);
+    try {
+      const updated = await api.updateKBADraft(
+        currentDraft.id,
+        { status: "draft" },
+        "user@example.com"
+      );
+      setCurrentDraft(updated);
+      setEditedDraft(JSON.parse(JSON.stringify(updated)));
+      setMessage({ type: "success", text: "✓ Zurück zu Entwurf" });
+    } catch (error) {
+      setMessage({ type: "error", text: "Fehler beim Status-Update" });
+    } finally {
+      setSaving(false);
+    }
+  };
+
   // Handler: Publish to Knowledge Base
   const handlePublish = async () => {
     if (!currentDraft) return;
@@ -1067,6 +1089,18 @@ export default function KBADrafterPage() {
                 </Button>
               )}
 
+              {/* Unreview Button (Reviewed Status) */}
+              {displayDraft.status === "reviewed" && (
+                <Button
+                  appearance="subtle"
+                  icon={<ArrowUndo24Regular />}
+                  onClick={handleUnreview}
+                  disabled={saving}
+                >
+                  Zurück zu Entwurf
+                </Button>
+              )}
+
               {/* Publish Button (Reviewed Status) */}
               {displayDraft.status === "reviewed" && (
                 <Button