Allow immediate customer signup without email delivery

[kcrmin]

What changed

• make email verification configurable and disabled by default for the current no-SES stage
• create new password accounts directly as active, login-ready accounts
• activate existing pending accounts on repeated signup without replacing their original password
• retain verification endpoints and persistence structures for future email delivery
• return verificationRequired=false when no verification token is issued

Why

SES is no longer available during the current development bootstrap. Requiring email verification left every new email/password account unable to log in.

Product authority: user:kcrmin — “SES 사라져서 이제 이메일 인증 하면 안되는거 아니야?” and “반영해주고 푸시까지 해줘”.

Validation

• focused application, controller, and PostgreSQL/Flyway persistence tests passed
• live Docker signup returned verificationRequired=false and immediate login issued an access token
• full backend suite reached 178 backend-api tests with one pre-existing unrelated failure: ExternalToolDelegatedEditJourneyIntegrationTest (NoSuchElementException at line 87); the same test fails alone on develop-based code