PART3: feat(settings): Migrate fxa-settings from GraphQL to direct auth-client (cutover)

[vbudhram]

Because

• The fxa-graphql-api service adds unnecessary latency and complexity between fxa-settings and fxa-auth-server
• GraphQL mutations/queries coupled the frontend to Apollo cache management, making state management harder to reason about
• Direct auth-client calls simplify the data flow and reduce the dependency surface

This pull request

• Removes ApolloProvider, ApolloClient, and all GQL mutations/queries from the fxa-settings entrypoint and page containers
• Replaces GQL calls with direct fxa-auth-client methods (signInWithAuthPW, getCredentialStatusV2,
  sendUnblockCode, etc.)
• Adds account-storage.ts — unified localStorage-based account state replacing the Apollo InMemoryCache
• Adds AccountStateContext and
  AuthStateContext React contexts for reactive state management
• Adds useAccountData hook that fetches account, profile, and attached clients data in parallel via auth-client
• Renames gql-key-stretch-upgrade to auth-key-stretch-upgrade, now calling auth-client directly
• Replaces Apollo cache with a no-op shim for remaining legacy references (gql.ts)
• Removes @apollo/client and graphql from fxa-settings dependencies
• Removes PageMfaGuardWithGqlTest (GQL-only test page)
• Updates all Signin, Signup, InlineTotpSetup, and InlineRecoverySetup containers and their tests

Issue

Closes: https://mozilla-hub.atlassian.net/browse/FXA-12995

Checklist

• My commit is GPG signed
• Tests pass locally (if applicable)
• Documentation updated (if applicable)
• RTL rendering verified (if UI changed)

Other Information

Scope: 90 files changed, ~2,600 insertions, ~2,700 deletions

Breaking changes: The fxa-graphql-api server is no longer required for fxa-settings to function. CSP rules for the GQL endpoint have been removed from content-server configuration.

Legacy shim: gql.ts and cache.ts retain a no-op Apollo cache shim for files not yet migrated (PostVerify, SetPassword, InlineRecoveryKeySetup). These should be cleaned up in a follow-up.