fix: 还原 .env.example 为 Neon.tech 变量，简化 docker-compose 移除未用的 postgres/redis 服务

Author: longsizhuo

.env.example

@@ -1,11 +1,18 @@
-# --- 数据库（本地 Docker postgres 服务）---
-POSTGRES_DB=involution_hell
-POSTGRES_USER=involution
-POSTGRES_PASSWORD=change_me
-SPRING_DATASOURCE_URL=jdbc:postgresql://postgres:5432/involution_hell
+# --- 数据库（Neon.tech 或其他 PostgreSQL）---
+PGHOST=ep-xxxx.ap-southeast-2.aws.neon.tech
+PGPORT=5432
+PGUSER=neondb_owner
+PGPASSWORD=change_me
+PGDATABASE=neondb
+PGSSLMODE=require
+
+# Spring Boot JDBC 连接（由上面的 PG 变量转换而来）
+SPRING_DATASOURCE_URL=jdbc:postgresql://ep-xxxx.ap-southeast-2.aws.neon.tech/neondb?sslmode=require
+SPRING_DATASOURCE_USERNAME=neondb_owner
+SPRING_DATASOURCE_PASSWORD=change_me
+SPRING_SQL_INIT_MODE=always
 
 # --- Spring Security OAuth2（GitHub 登录）---
-# 从 GitHub Developer Settings 获取
 AUTH_GITHUB_ID=
 AUTH_GITHUB_SECRET=
 AUTH_SECRET=
@@ -16,10 +23,16 @@ OPENAI_API_URL=https://api.openai.com/v1
 OPENAI_MODEL=gpt-4.1
 
 # --- 应用基本设置 ---
-SERVER_PORT=8080
 SPRING_APPLICATION_NAME=backend
+SERVER_PORT=8080
+SPRING_PROFILES_ACTIVE=default
 SPRING_SQL_INIT_MODE=always
 
+# --- Actuator ---
+MANAGEMENT_ENDPOINTS_WEB_EXPOSURE_INCLUDE=health,info,metrics
+MANAGEMENT_ENDPOINT_HEALTH_PROBES_ENABLED=true
+MANAGEMENT_ENDPOINT_HEALTH_SHOW_DETAILS=always
+
 # --- 网关（Caddy）---
 CADDY_SITE_ADDRESS=:80
 CADDY_HTTP_PORT=80