feat(ui): distinguish dev/prod via VITE_DEPLOY_ENV

Both instances run with NODE_ENV=production, so import.meta.env.PROD was
always true and the header always showed 'Production'. deploy.sh now passes
VITE_DEPLOY_ENV=<branch> into the build and Header reads it to label the
system indicator dev vs prod correctly.

deploy/deploy.sh

@@ -16,7 +16,7 @@ git fetch --prune origin
 git checkout "$BRANCH"
 git pull --ff-only origin "$BRANCH"
 npm ci
-npm run build
+VITE_DEPLOY_ENV="$BRANCH" npm run build
 sudo systemctl restart "$SVC"
 echo "Deployed $BRANCH ($SVC). Status:"
 systemctl --no-pager status "$SVC" | head -n 5