Add ability to fetch available models from third-party aggregation
providers (SiliconFlow, OpenRouter, etc.) via OpenAI-compatible
GET /v1/models endpoint. Users can click "Fetch Models" button in
the provider form, then select models from a dropdown on each
model input field.
- Backend: new model_fetch service + Tauri command (Rust)
- Frontend: ModelInputWithFetch shared component
- Integrated into all 5 app forms (Claude/Codex/Gemini/OpenCode/OpenClaw)
- i18n support for zh/en/ja