fix(docker): create .env file in Dockerfile instead of copying

- Create .env file with RUN echo instead of COPY

- .env is in .gitignore so cannot be copied

Dockerfile

@@ -7,15 +7,14 @@ ENV PLAYWRIGHT_SKIP_BROWSER_DOWNLOAD=1
 ENV CYPRESS_INSTALL_BINARY=0
 ENV NODE_ENV=production
 
-# Set API URL for build
-ENV GATEWAY_URL=http://localhost:9100
+# Set API URL for build (create .env file)
+RUN echo "GATEWAY_URL=http://localhost:9100" > .env
 
 # Install build dependencies
 RUN apt-get update && apt-get install -y python3 make g++ git && rm -rf /var/lib/apt/lists/*
 
 # Copy package files
 COPY package*.json ./
-COPY .env ./
 
 # Install dependencies
 RUN npm ci --legacy-peer-deps --prefer-offline --no-audit