Add Email Verification

[LuoPengcheng12138]

Description

• For C-end users: Click "signup" to redirect to the https://www.eigent.ai/signup page
• For enterprise users: Click "signup" to redirect to the enterprise authentication page (not implemented)
• For local users: Usernames and passwords are stored in Docker volumes; clicking "signup" remains as-is, and email verification is not required

What is the purpose of this pull request?

• [ ] Bug fix
• [x] New Feature
• [ ] Documentation update
• [ ] Other