Switch viewer PM2 template to next start and add deploy-viewer.sh.

DEV should build once then run production Next.js instead of long-lived next dev.

scripts/deploy-viewer.sh

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+# Build viewer for production and restart PM2 process.
+# Usage: ./scripts/deploy-viewer.sh [--skip-install]
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+VIEWER="$ROOT/viewer-frontend"
+SKIP_INSTALL=0
+for arg in "$@"; do
+  case "$arg" in
+    --skip-install) SKIP_INSTALL=1 ;;
+  esac
+done
+
+cd "$VIEWER"
+if [[ "$SKIP_INSTALL" -eq 0 ]]; then
+  npm ci --prefer-offline
+fi
+npm run build
+
+cd "$ROOT"
+if pm2 describe punimtag-viewer >/dev/null 2>&1; then
+  pm2 restart punimtag-viewer --update-env
+else
+  pm2 start ecosystem.config.js --only punimtag-viewer
+fi
+
+echo "Viewer deployed (next start). Logs: pm2 logs punimtag-viewer --lines 30"