Fix App Store password auth with updated native auth endpoint

[yuhao7370]

Fix App Store password auth with updated native auth endpoint

Summary

This PR fixes the App Store IPA download flow when authenticating with only an Apple ID and password.

Apple's App Store authentication flow now returns and expects the newer native auth endpoint:

https://auth.itunes.apple.com/auth/v1/native/fast/

The old buy.itunes.apple.com/.../authenticate path can return empty or non-plist responses, which causes plistlib.InvalidFileException and prevents the tool from obtaining a valid download URL.

Changes

• Resolve authenticateAccount from the init bag, including the newer root-level field.
• Normalize Apple's native auth endpoint to /auth/v1/native/fast/.
• Update the Configurator User-Agent used for auth requests.
• Add fallback candidates for older auth endpoints.
• Follow auth redirects with proper relative URL handling.
• Parse plist responses more defensively, including wrapped Document, plist, and dict payloads.
• Improve error reporting for empty, rate-limited, and non-plist Apple responses.
• Support auth responses that provide dsPersonId instead of download_queue_info.dsid.
• Preserve Apple pod information and use the pod-specific App Store host for download/purchase requests.
• Avoid sending an empty externalVersionId when no version id is requested.
• Update retry-auth handling to skip the new auth host correctly.
• Use the normalized plist parser when checking auth failures.