[umbrella for appDir migration] Add missing routes to App Router for /auth route group

[hbjORbj]

Nested Routes under /auth route group:

• auth/verify.tsx chore: App-router-migration(/auth/verify) add missing metadata / page & extract components into /module #16444
• auth/verify-email.tsx
• auth/verify-email-change.tsx chore: App-router-migration(/auth/verify) add missing metadata / page & extract components into /module #16444
• auth/signin.tsx
• auth/saml-idp.tsx chore: App-router-migration /auth/new and /auth/saml-idp #16447
• auth/new.tsx chore: App-router-migration /auth/new and /auth/saml-idp #16447
• auth/error.tsx chore: App-router-migration /auth/error, /auth/platform, /auth/oauth2 #16445
• auth/forgot-password/**/*
• auth/oauth2/**/* chore: App-router-migration /auth/error, /auth/platform, /auth/oauth2 #16445
• auth/platform/**/* chore: App-router-migration /auth/error, /auth/platform, /auth/oauth2 #16445
• auth/setup/**/*
• auth/sso/**/*