[codex] guard settings API key entries

[chaochaoweb3]

Summary

• normalize API key entries before rendering the settings key list
• support both string keys and object entries with key/value fields
• use the normalized string for display and delete confirmation

Fixes #302

Validation

• npm run typecheck
• npm exec -- vitest run src/components/settings/SettingsPage.test.ts
• npm exec -- eslint src/components/settings/SettingsPage.tsx src/components/settings/SettingsPage.test.ts src/components/settings/apiKeys.ts
• git diff --check

Note: full npm run lint still fails on existing unrelated files: ChatPanel.tsx, PortConfig.tsx, ProxySettings.tsx, and several context exports.