Mehrere Auswahlen in einem Objekt speichern

- Neues JSON-Feld 'selections' in Directus objects-Collection
- Alle Auswahlen (bbox/polygon) landen in einem einzigen Objekt
- Erste Auswahl bleibt weiterhin in bbox/polygon für Kompatibilität
- GET-Proxy liefert selections-Feld mit aus

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

frontend/src/pages/DrawIt.tsx

@@ -88,24 +88,21 @@ export default function DrawIt() {
     if (!currentPicture || !token || currentSelections.length === 0) return
     setSaving(true)
     try {
-      // Save one object per selection
-      const newObjs: DirectusObject[] = []
-      for (const sel of currentSelections) {
-        const obj = await createDirectusObject({
-          picture: currentPicture.id,
-          bbox: sel.mode === 'rect' ? (sel.bbox ?? null) : null,
-          polygon: sel.mode === 'polygon' ? (sel.polygon ?? null) : null,
-          user_notes: userNotes.trim() || null,
-          parent: parentId,
-        }, token)
-        newObjs.push({ ...obj, visible: true })
-      }
-      setObjects(prev => [...prev, ...newObjs])
+      const first = currentSelections[0]
+      const obj = await createDirectusObject({
+        picture: currentPicture.id,
+        bbox: first.mode === 'rect' ? (first.bbox ?? null) : null,
+        polygon: first.mode === 'polygon' ? (first.polygon ?? null) : null,
+        selections: currentSelections,
+        user_notes: userNotes.trim() || null,
+        parent: parentId,
+      }, token)
+      setObjects(prev => [...prev, { ...obj, visible: true }])
       setCurrentSelections([])
       setUserNotes('')
       setParentId(null)
       canvasRef.current?.resetSelection()
-      showStatus(`${newObjs.length} Objekt(e) gespeichert.`)
+      showStatus('Objekt gespeichert.')
     } catch (e) {
       showStatus(e instanceof Error ? e.message : 'Fehler beim Speichern.', true)
     } finally {