feat: add Codex support to ProviderForm

- Create useCodexConfigState hook for managing Codex configuration
  - Handles auth.json (JSON) and config.toml (TOML) separately
  - Bidirectional sync with Base URL extraction
  - API Key management from auth.OPENAI_API_KEY
- Integrate Codex-specific UI components
  - Codex API Key input
  - Codex Base URL input with endpoint speed test
  - CodexConfigEditor for auth/config editing
- Update handlePresetChange to support Codex presets
- Update handleSubmit to compose Codex auth+config
- Conditional rendering: Claude uses JsonEditor, Codex uses CodexConfigEditor

src/components/providers/forms/hooks/index.ts

@@ -2,3 +2,4 @@ export { useProviderCategory } from "./useProviderCategory";
 export { useApiKeyState } from "./useApiKeyState";
 export { useBaseUrlState } from "./useBaseUrlState";
 export { useModelState } from "./useModelState";
+export { useCodexConfigState } from "./useCodexConfigState";