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

CHANGELOG.md

@@ -16,15 +16,25 @@ version tags are cut in this repo — POC stage, `main` is the release line).
 - `delivery_orders` table + additive `batches` columns (`plate`, `do_numbers`,
   `expected_*`, `net_*`); photo tree `do_photos/YYYY-MM-DD/` (7-day retention).
 - APIs: `POST /api/batch/stop-preview`, DO CRUD + `POST /api/do/upload`,
-  `GET|POST /api/do/settings` (office-only plate/do flags; **ocr_engine both
-  ports**), office-only mode/model_mode POST (403 on operator; 409 when batch active).
+  `GET|POST /api/do/settings` (all gated fields office-only:
+  require_plate/require_do/**ocr_engine**, 403 on operator), office-only
+  mode/model_mode POST (403 on operator; 409 when batch active).
 - `src/do_batch.py` (pure gates/nets/units), `src/do_ocr.py`
-  (`extract_do_fields` tesseract|paddle|none).
-- Operator DO panel + OCR toggle; monitoring 3-way mode switch + model mode +
-  OCR/require-plate controls; history/export plate, DO, expected, net columns.
+  (`extract_do_fields` rapid|tesseract|paddle|none).
+- **RapidOCR default engine** (`rapidocr_onnxruntime`, bundled PP-OCR models);
+  tesseract + paddle kept as backups, explicit error if a dep is missing.
+- Operator DO panel (no OCR toggle); monitoring 3-way mode switch + model mode +
+  OCR selector with labels `RapidOCR (Default, Light & Accurate)` /
+  `Tesseract (Backup, Light)` / `PaddleOCR (Accuracy, Heavy to run)` /
+  `None (Manual)` + require-plate controls; history/export plate, DO,
+  expected, net columns.
 - `ERD.md` (Mermaid ERD, repo root; superseded `docs/do-erd.md`); tests `tests/test_do_batch.py`.
 
 ### Changed
+- OCR engine default **`rapid`** (was `tesseract`) across `config.yaml`,
+  `DoConfig`, `empty_do_settings`, `extract_do_fields`; `ocr_engine` write
+  moved office-only (was both ports); OCR engine selector removed from
+  operator page.
 - Default batch mode seed **`auto`** (was hard-coded `manual` when
   `batch_mode.json` missing); `predict.py` accepts `do_manual` as operator-driven
   and persists sack `unloading` for net-at-stop.