feat: RapidOCR default OCR engine, office-only ocr_engine, drop operator toggle

AGENTS.md

@@ -37,8 +37,8 @@ Indonesian (`karung`=sack, `truk`=truck); YOLO class names are English
   `batch_mode.json` keeps only batch flow mode (`auto`|`do_manual`|`manual`,
   default seed `batch.default_mode: auto`).
   **Port split:** `mode` / `model_mode` / `require_plate` / `require_do` POSTs →
-  office `:5721` only (403 on `:5000`); **`ocr_engine` POST both ports** (synced
-  via `GET /api/do/settings`). Discard batch only if **both** `net_sack==0` and
+  office `:5721` only (403 on `:5000`); **`ocr_engine` office-only too**
+  (default `rapid`). Discard batch only if **both** `net_sack==0` and
   `net_box==0`. DO helpers: `src/do_batch.py`, OCR: `src/do_ocr.py`;
   ERD: `ERD.md` (repo root).
 - **Counting filters by class name, not ID**: `SackDetector`/`BoxDetector`/