fix(admin-web): add API_GATEWAY_URL env var for Docker build

The Next.js rewrites in next.config.js require API_GATEWAY_URL to be set
at build time. Added this environment variable to both Dockerfile and
docker-compose.yml to ensure proper routing to Kong gateway in production.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/mining-admin-web/Dockerfile

@@ -24,6 +24,8 @@ COPY . .
 # 设置环境变量
 ENV NEXT_TELEMETRY_DISABLED=1
 ENV NODE_ENV=production
+# 设置 API 网关地址（构建时需要，用于 next.config.js rewrites）
+ENV API_GATEWAY_URL=https://rwaapi.szaiai.com
 
 # 构建应用
 RUN npm run build

frontend/mining-admin-web/docker-compose.yml

@@ -13,6 +13,7 @@ services:
       - NODE_ENV=production
       - PORT=3100
       - NEXT_TELEMETRY_DISABLED=1
+      - API_GATEWAY_URL=https://rwaapi.szaiai.com
       - NEXT_PUBLIC_API_URL=${NEXT_PUBLIC_API_URL:-http://localhost:3023}
       - NEXT_PUBLIC_APP_NAME=挖矿管理后台
     healthcheck: