Initialize project and update portal port configuration

Set default portal port to 8081, fix Dart build issue in cart screen, and update setup documentation.

Co-Authored-By: Oz <oz-agent@warp.dev>

docker/entrypoint/30-generate-runtime-config.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+set -eu
+
+TARGET="/usr/share/nginx/html/assets/assets/config/runtime_config.json"
+mkdir -p "$(dirname "$TARGET")"
+
+if command -v envsubst >/dev/null 2>&1; then
+  envsubst < /opt/runtime_config.template.json > "$TARGET"
+else
+  cat > "$TARGET" <<JSON
+{
+  "firebase_api_key": "${FIREBASE_API_KEY:-}",
+  "firebase_auth_domain": "${FIREBASE_AUTH_DOMAIN:-}",
+  "firebase_project_id": "${FIREBASE_PROJECT_ID:-}",
+  "firebase_storage_bucket": "${FIREBASE_STORAGE_BUCKET:-}",
+  "firebase_messaging_sender_id": "${FIREBASE_MESSAGING_SENDER_ID:-}",
+  "firebase_app_id": "${FIREBASE_APP_ID:-}",
+  "firebase_measurement_id": "${FIREBASE_MEASUREMENT_ID:-}"
+}
+JSON
+fi