feat: object words in left sidebar + suggestions in pair form

- Backend: GET /api/directus/db-objects/<id>/words via db_objects_db_words
- GenerateIt: load objectWords on object select, show as chips in left sidebar
- PairForm: show object words as clickable suggestion chips above word input
  (click to add, greyed out if already added)

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

frontend/src/api.ts

@@ -454,6 +454,15 @@ export async function createDbPair(
   return data
 }
 
+export async function getDbObjectWords(objectId: string, token: string): Promise<DbWord[]> {
+  const res = await fetch(`/api/directus/db-objects/${objectId}/words`, {
+    headers: { Authorization: `Bearer ${token}` },
+  })
+  const data = await res.json()
+  if (!res.ok) throw new Error('Fehler beim Laden der Objekt-Wörter')
+  return data.data as DbWord[]
+}
+
 export async function updateDbPair(
   pairId: string,
   payload: { level?: number; question_de?: string; statement_de?: string },