Add cross-dashboard header links (UPLOAD_DASHBOARD_URL, LIVE_DASHBOARD_URL)

SPEC.md

@@ -54,6 +54,7 @@ env: MIN_OBJECT_PER_BATCH → min count to persist batch (default 60)
 env: MIN_DURATION_PER_BATCH → min seconds to persist batch (default 60)
 env: LIVE_STREAM_ENABLED → write annotated JPEG snapshot each N frames
 env: EXPORT_CSV → write per-crossing CSV (default true)
+env: UPLOAD_DASHBOARD_URL → header link to upload recounting dashboard (default empty → hidden)
 
 ### Recounting dashboard config
 ```
@@ -70,6 +71,7 @@ env: RECOUNTING_UPLOAD_PORT → port for upload UI (default 5003)
 env: UPLOAD_DIR → dir for uploaded MP4s (default <repo>/uploads)
 env: RECOUNT_CMD → replay command template with {path} placeholder (default "bytetrack-counter config.env --source {path}")
 env: RECOUNTING_UPLOAD_TEMPLATE → template (default recounting_upload.html)
+env: LIVE_DASHBOARD_URL → header link to live counter dashboard (default empty → hidden)
 ```
 ```
 
@@ -178,6 +180,7 @@ T12|x|add recounting dashboard — dual-API counter panels, MP4 browser, go2rtc
 T13|x|add template system — DASHBOARD_TEMPLATE env var selects dashboard.html|lamborghini|tesla|
 T14|x|harden reset API — separate SHM marker creation from state file cleanup; return 500 on SHM failure|V20
 T15|x|add upload recounting dashboard — MP4 upload, progress bar, RECOUNT_CMD replay|V21
+T16|x|add cross-dashboard header links — UPLOAD_DASHBOARD_URL (live→upload) & LIVE_DASHBOARD_URL (upload→live)|I.config
 ```
 
 ## §B — Bugs