Add developer team selection

[chenx-dust]

Summary

• prompt users to choose a developer team when an Apple ID belongs to multiple teams
• reuse the selected team for signing, certificate, and App ID operations during the login session
• show the active developer team below the logged-in account
• add English, Simplified Chinese, Traditional Chinese, and Cantonese copy for the new UI

Why

iloader previously used the first team returned by Apple's listTeams endpoint. Accounts belonging to multiple teams could therefore sign with an unintended team and had no way to confirm which team was active.

User impact

Accounts with one team continue without interruption. Accounts with multiple teams must select one during login; canceling or timing out aborts the login instead of silently choosing a team. The selected team name remains visible in the account card for the session.

Validation

• cargo check
• cargo fmt --check
• npm run build
• git diff --check

[chenx-dust]

This PR is drafted by GPT 5.6 Sol, and verified by human.