Add Email Verification Service for Signup

Description: Implement a separate microservice to handle email verification for new user signups.

Acceptance Criteria:

• When a user signs up, send a verification email with a unique link or token.
• Users cannot fully register or log in until their email is verified.
• If email verification fails or token is invalid/expired, show an error message on the signup/login page.
• Service should be independent (microservice) and communicate with main backend via API.

Optional Enhancements:

• Resend verification email option. (NOT NEEDED NOW)
• Expiry time for verification tokens.

Depends on: None – can be implemented independently.