fix: 统一数据库默认密码 change_me → cyrene_pass

Docker Compose 和 .env 使用 cyrene_pass，但 5 个 Go 源码文件
和 DevTools config.js 中的 fallback 密码仍是 change_me，
导致 memory-service/tool-engine/gateway 启动后 DB 认证失败。
修复 7 个文件中的硬编码 fallback 密码，统一为 cyrene_pass。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

devtools/src/config.js

@@ -93,7 +93,7 @@ export const SERVICES = {
     command: './main',
     env: {
       PORT: '8091',
-      DB_URL: process.env.DB_URL || 'postgres://cyrene:change_me@localhost:5432/cyrene_ai?sslmode=disable',
+      DB_URL: process.env.DB_URL || 'postgres://cyrene:cyrene_pass@localhost:5432/cyrene_ai?sslmode=disable',
     },
     healthUrl: 'http://localhost:8091/api/v1/health',
     port: 8091,
@@ -107,7 +107,7 @@ export const SERVICES = {
     command: './main',
     env: {
       PORT: '8092',
-      DB_URL: process.env.DB_URL || 'postgres://cyrene:change_me@localhost:5432/cyrene_ai?sslmode=disable',
+      DB_URL: process.env.DB_URL || 'postgres://cyrene:cyrene_pass@localhost:5432/cyrene_ai?sslmode=disable',
       IOT_SERVICE_URL: process.env.IOT_SERVICE_URL || process.env.IOT_DEBUG_SERVICE_URL || 'http://localhost:8083',
     },
     healthUrl: 'http://localhost:8092/api/v1/health',