refactor(n8n): 移除环境变量配置简化本地部署流程

- 删除 .env.example 文件，将默认配置直接写入 docker-compose.yml
- 更新 .gitignore 添加 .idea 目录忽略
- 修改 docker-compose.yml 将环境变量硬编码为默认值
- 移除 README.md 中关于复制 .env.example 的说明
- 添加 Mac 平台兼容性配置说明和可选参数设置

docker-compose.yml

@@ -4,14 +4,14 @@ services:
     container_name: n8n-postgres
     restart: unless-stopped
     environment:
-      POSTGRES_USER: ${POSTGRES_USER}
-      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD}
-      POSTGRES_DB: ${POSTGRES_DB}
-      TZ: ${TZ}
+      POSTGRES_USER: n8n
+      POSTGRES_PASSWORD: n8npass
+      POSTGRES_DB: n8n
+      TZ: Asia/Shanghai
     volumes:
       - ./postgres-data:/var/lib/postgresql/data
     healthcheck:
-      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER} -d ${POSTGRES_DB}"]
+      test: ["CMD-SHELL", "pg_isready -U n8n -d n8n"]
       interval: 10s
       timeout: 5s
       retries: 5
@@ -21,15 +21,18 @@ services:
     container_name: n8n
     restart: unless-stopped
     ports:
-      - "${N8N_PORT}:5678"
+      - "5678:5678"
+    # Mac 上如遇 `Restarting (139)` 可开启以下两项：
+    # platform: linux/amd64
+    # user: "0:0"
     environment:
       DB_TYPE: postgresdb
       DB_POSTGRESDB_HOST: postgres
       DB_POSTGRESDB_PORT: 5432
-      DB_POSTGRESDB_DATABASE: ${POSTGRES_DB}
-      DB_POSTGRESDB_USER: ${POSTGRES_USER}
-      DB_POSTGRESDB_PASSWORD: ${POSTGRES_PASSWORD}
-      TZ: ${TZ}
+      DB_POSTGRESDB_DATABASE: n8n
+      DB_POSTGRESDB_USER: n8n
+      DB_POSTGRESDB_PASSWORD: n8npass
+      TZ: Asia/Shanghai
     volumes:
       - ./n8n-data:/home/node/.n8n
     depends_on: