Title: Feature Request: Custom OpenAI-Compatible API Connector

Description:

Currently, 闪电说 语音输入only supports a fixed set of AI providers (Volcano Engine, Alibaba Cloud).

I'd like to request the ability to add custom OpenAI-compatible API endpoints (Base URL + API Key).

Why this matters:

• Users in different regions have different accessibility (e.g., OpenRouter works in HK/overseas but not mainland China; some users prefer Silicon Flow, Moonshot, or self-hosted models)

• Power users run their own AI agents (WorkBuddy, n8n, local LLMs) and want voice commands to trigger them

• This would make 闪电说 a universal voice command center, not just an input method

Minimal viable design:

• New setting: "Custom API" with fields for Base URL, API Key, and Model ID

• Compatible with OpenAI API format (works with OpenRouter, Silicon Flow, Ollama, vLLM, etc.)

• Optional: Webhook skill type to trigger external agent workflows

This would be a unique differentiator vs. competitors like 豆包输入法.