Remove waitlist text and fix last used badge bug

[mattdjenkinson]

Overview

This PR introduces a "last used" badge for identity provider (IDP) login buttons, improves the registration/waitlist UI copy, and adds i18n support across all locale files.

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Features

1. Last Used Badge on IDP Buttons

• What: A "Last used" badge appears on the identity provider (Google, Apple, GitHub, etc.) that the user last successfully signed in with.
• Storage: The last-used IDP ID is stored in an HTTP-only cookie (last-used-idp-id) with a 1-year expiry.
• When it's set: The cookie is only set when authentication completes successfully—not when the user merely clicks an IDP button.
• Where it appears: The badge is shown on IDP buttons across:
  • Login name page
  • IDP selection page
  • Register page
  • Authenticator setup page
  • IDP link page

Technical details:

• Cookie helpers: setLastUsedIdpId() and getLastUsedIdpId() in lib/cookies.ts
• Cookie is set in:
  • createNewSessionFromIdpIntent (when returning redirect, including email verification and MFA flows)
  • registerUserAndLinkToIDP (when registration with IDP linking succeeds)
• idpId is passed through the success flow: success page → loginSuccess/linkingSuccess → IdpSignin → createNewSessionFromIdpIntent
• BaseButton shows the badge when isLastUsed is true; custom props are destructured to avoid passing them to the DOM

2. Registration / Waitlist UI Updates

• Register page: Uses the new waitlist namespace with title, subtitle, and description for clearer hierarchy.
• Login button: Removed the waitlist question/info block from the register page footer.
• Layout: Title in h3, subtitle in h1, description in p for improved visual hierarchy.

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Locale Updates

All locale files (de, es, it, pl, ru, zh) were updated to match en.json:

Key	Description
loginname.register	"Create account" (was "Register new user" etc.)
waitlist.title	"Welcome!"
waitlist.subtitle	"Let's get you started"
waitlist.description	"Create your free account with just a few details"
register.alreadyRegistered	"Already have an account?"
register.loginNow	"Log in here."
idp.lastUsed	"Last used" (for the IDP badge)

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Files Changed

Core Feature

• apps/login/src/lib/cookies.ts – Cookie helpers for last-used IDP
• apps/login/src/components/idps/base-button.tsx – Badge UI and prop handling
• apps/login/src/components/sign-in-with-idp.tsx – Pass lastUsedIdpId and isLastUsed
• apps/login/src/components/idp-signin.tsx – Pass idpId to session creation
• apps/login/src/components/idps/pages/login-success.tsx – Pass idpId to IdpSignin
• apps/login/src/components/idps/pages/linking-success.tsx – Pass idpId to IdpSignin
• apps/login/src/lib/server/idp.ts – Set cookie on success, pass idpId through flow
• apps/login/src/lib/server/register.ts – Set cookie on successful IDP registration
• apps/login/src/app/(main)/(boxed)/idp/[provider]/success/page.tsx – Pass idpId to success components

Pages Using SignInWithIdp (pass lastUsedIdpId)

• apps/login/src/app/(main)/(illustration)/loginname/page.tsx
• apps/login/src/app/(main)/(boxed)/idp/page.tsx
• apps/login/src/app/(main)/(illustration)/register/page.tsx
• apps/login/src/app/(main)/(boxed)/authenticator/set/page.tsx
• apps/login/src/app/(main)/(boxed)/idp/link/page.tsx

UI Updates

• apps/login/src/app/(main)/(illustration)/register/page.tsx – Waitlist title/subtitle/description
• apps/login/src/app/(main)/(illustration)/register/_login-btn.tsx – Removed waitlist block

Locales

• apps/login/locales/de.json
• apps/login/locales/en.json
• apps/login/locales/es.json
• apps/login/locales/it.json
• apps/login/locales/pl.json
• apps/login/locales/ru.json
• apps/login/locales/zh.json