chore: update default account and add example data

- Update default login email to xinmi@local.com
- Update default password to 12345678 (and bcrypt hash in crm.sql)
- Add example customers, products, and contracts to init SQL
- Fix Docker env interpolation for VITE_API_BASE_URL
- Hardcode local backend API URL in frontend .env files
- Update README and docs to reflect new default credentials

docs/docs/project/devops/deploy-cloudserver.md

@@ -484,7 +484,7 @@ file:
 mail:
   smtp: smtp.qq.com
   secret: dhsepilzlvoaceij   // 改成自己的QQ邮箱SMTP服务的授权码
-  sender: 1655064994@qq.com  // 改成自己的QQ邮箱
+  sender: xinmi@local.com  // 改成自己的QQ邮箱
 ```
 
 **如何开启邮箱的 SMTP 服务并获取授权码？**

docs/docs/project/docs/deploy-guide.md

@@ -51,7 +51,7 @@ file:
 mail:
   smtp: smtp.qq.com
   secret: dhsepilzlvoaceij   // 改成自己的QQ邮箱SMTP服务的授权码
-  sender: 1655064994@qq.com  // 改成自己的QQ邮箱
+  sender: xinmi@local.com  // 改成自己的QQ邮箱
 ```
 
 **如何开启邮箱的 SMTP 服务并获取授权码？**