[codex] Add account deletion feedback

[jjoonleo]

Summary

• Add anonymized account deletion feedback storage independent from the User table
• Accept optional deletion feedback on general, Google, and Apple account deletion endpoints
• Hash deleted-user emails and preserve deleted user id, social type, message, and timestamp
• Document the account deletion API for frontend integration
• Fix duplicate Google relogin handling after account deletion by authenticating JWTs by user id, making refresh tokens unique, and serializing concurrent Google login/register requests per Google account

Validation

• ./gradlew compileJava compileTestJava test --tests devkor.ontime_back.global.jwt.JwtTokenProviderTest --tests devkor.ontime_back.controller.UserAuthControllerTest

Notes

• The previous PR was merged into deploy. This new PR targets main.
• Any duplicate user rows already created in production still need one-time cleanup.