fix(draw): Bildnavigation debounce – nur letztes Bild laden bei schnellem Weiterklicken

currentPicture folgt debouncedIndex (350ms), currentIndex reagiert sofort
für Counter und Button-Disabled-State.

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

frontend/src/pages/DrawIt.tsx

@@ -30,6 +30,7 @@ export default function DrawIt() {
 
   const [pictureList, setPictureList] = useState<DirectusPicture[]>([])
   const [currentIndex, setCurrentIndex] = useState(-1)
+  const [debouncedIndex, setDebouncedIndex] = useState(-1)
   const [objects, setObjects] = useState<DirectusObject[]>([])
   const [selectedObjectId, setSelectedObjectId] = useState<string | null>(null)
   const [currentSelections, setCurrentSelections] = useState<Selection[]>([])
@@ -52,6 +53,12 @@ export default function DrawIt() {
 
   const canvasRef = useRef<DrawCanvasHandle>(null)
 
+  // Debounce: Bild erst laden wenn 350ms keine weitere Navigation
+  useEffect(() => {
+    const t = setTimeout(() => setDebouncedIndex(currentIndex), 350)
+    return () => clearTimeout(t)
+  }, [currentIndex])
+
   useEffect(() => {
     if (safeWordInputVisible) safeWordInputRef.current?.focus()
   }, [safeWordInputVisible])
@@ -83,8 +90,9 @@ export default function DrawIt() {
     }
   }
 
+  // currentPicture folgt dem debouncedIndex → lädt erst wenn Navigation pausiert
   const currentPicture: DirectusPicture | null =
-    currentIndex >= 0 && currentIndex < pictureList.length ? pictureList[currentIndex] : null
+    debouncedIndex >= 0 && debouncedIndex < pictureList.length ? pictureList[debouncedIndex] : null
 
   // Map DirectusObject → CanvasObject for rendering
   const canvasObjects: CanvasObject[] = objects.map((obj, i) => ({