Add cross-dashboard header links (UPLOAD_DASHBOARD_URL, LIVE_DASHBOARD_URL)

AGENTS.md

@@ -48,6 +48,7 @@ PYTHONNOUSERSITE=1 venv/bin/python recounting_dashboard_upload.py
 - **Reset flow**: `POST /api/reset` → deletes state JSON + touches `{SHM_DIR}/.reset`. `batch_store._check_reset_signal()` watches this marker and clears in-memory state on next crossing.
 - **Upload filename contract**: uploads are expected as `batch_XX_YYYYMMDD_HHmmSS.mp4` (XX = batch number, timestamp = date). `recounting_dashboard_upload.py` parses both to query the live API's `/api/day-detail/<YYYY-MM-DD>` for the recorded count.
 - **`RECOUNT_CMD`** in the upload dashboard is a template with a `{path}` placeholder, e.g. `bytetrack-counter config.env --source {path}`; the uploaded file path is `shlex.quote()`d before substitution.
+- **Cross-dashboard header links**: `UPLOAD_DASHBOARD_URL` (live → upload dashboard, `counter_dashboard.py`) and `LIVE_DASHBOARD_URL` (upload → live dashboard, `recounting_dashboard_upload.py`); empty value hides the header link.
 
 ## Code conventions