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>

uninstall_portal.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+set -Eeuo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_DIR="$SCRIPT_DIR"
+COMPOSE_FILE="$PROJECT_DIR/docker-compose.yml"
+ENV_FILE="$PROJECT_DIR/.env"
+FORCE=0
+
+if [[ "${1:-}" == "--force" ]]; then
+  FORCE=1
+fi
+
+if [[ $FORCE -eq 0 ]]; then
+  echo "WARNING: This will remove the Flutter portal containers, local images, and volumes for this project."
+  read -r -p "Continue? [y/N]: " answer
+  if [[ ! "$answer" =~ ^[Yy]$ ]]; then
+    echo "Uninstall cancelled."
+    exit 0
+  fi
+fi
+
+if [[ -f "$COMPOSE_FILE" ]]; then
+  if [[ -f "$ENV_FILE" ]]; then
+    docker compose -f "$COMPOSE_FILE" --env-file "$ENV_FILE" down --remove-orphans --volumes --rmi local || true
+  else
+    docker compose -f "$COMPOSE_FILE" down --remove-orphans --volumes --rmi local || true
+  fi
+fi
+
+docker container rm -f flutter_ecommerce_portal_web >/dev/null 2>&1 || true
+
+echo "Cleanup complete for flutter_ecommerce_portal."