feature: add google.oauth.enabled flag and seed default roles for Google…

[abhigyan24-ops]

Summary

Closes #45

Changes

1. google.oauth.enabled property flag

• Added google.oauth.enabled=${GOOGLE_OAUTH_ENABLED:true} to both
  application.properties and application-dev.properties
• GoogleAuthService now checks this flag at runtime and throws a clear
  BusinessException if Google Auth is disabled, instead of failing silently

2. DataInitializer — seed default roles on startup

• New DataInitializer component runs on startup via CommandLineRunner
• Creates ADMIN, RESTAURANT_OWNER, and CUSTOMER roles if they don't exist
• Prevents "CUSTOMER role not found" error during first Google OAuth login
• Idempotent — safe to run multiple times

How to enable/disable Google Auth

Set in environment or properties file:

• GOOGLE_OAUTH_ENABLED=true → Google login enabled (default)
• GOOGLE_OAUTH_ENABLED=false → Google login disabled, returns 400 with clear message

How to test

1. Set GOOGLE_OAUTH_ENABLED=false → POST /api/v1/auth/google returns 400
2. Set GOOGLE_OAUTH_ENABLED=true + valid GOOGLE_OAUTH_CLIENT_ID → Google login works
3. On fresh DB, roles are auto-created on startup

[rdodiya]

Hi @abhigyan24-ops ,
Please delete DataInitializer class as we are using DB authentication now, previously we were using in memory authenticaiton.

Also add a flag in frontend side in login, when the flag is disable the google authenticaiton button should not be shown in UI