feat: batch clip download from motionEye (trim+concat, history Klip button)

CHANGELOG.md

@@ -29,6 +29,9 @@ version tags are cut in this repo — POC stage, `main` is the release line).
   `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 - `ERD.md` (Mermaid ERD, repo root; superseded `docs/do-erd.md`); tests `tests/test_do_batch.py`.
+- History `Klip` button → office-only `GET /api/batch-clip/<date>/<batch_number>`
+  trims+concatenates motionEye recordings to the batch window (`src/clip.py`),
+  download `b<n>-<date>-<HH-MM-SS>.mp4`.
 
 ### Changed
 - OCR engine default **`rapid`** (was `tesseract`) across `config.yaml`,