feat: Add support for the OpenRouter.

[L-excellence]

关联 issue 链接：#12

变更说明：

1. 安装 AI SDK 接入 OpenRouter 的模块

pnpm install @openrouter/ai-sdk-provider -w

2. 在 AI 工作流程中接入 OpenRouter 供应商模型逻辑

...
+ import { createOpenRouter } from "@openrouter/ai-sdk-provider"

export const getAIClient = (provider: AIProvider, model: string) => {
  const modelConfig = findModelConfig(provider, model)

  switch (provider) {
    ...
+   case "openrouter":
+     return createOpenRouter({
+       baseURL: modelConfig.baseURL,
+       apiKey: modelConfig.apiKey,
+     }).chat(modelConfig.model)
    default:
      throw new Error(`Unsupported AI provider: ${provider}`)
  }
}

3. 在 data/config.template.json 模型配置文件中加入 OpenRouter 常用模型

{
    "providers": [
        ... 
+       {
+         "provider": "openrouter",
+         "models": [
+           {
+             "model": "anthropic/claude-3.7-sonnet",
+             "title": "Claude 3.7 Sonnet",
+             "baseURL": "https://openrouter.ai/api/v1",
+             "features": ["vision"],
+             "apiKey": "sk-****"
+           },
+           ...
+         ]
+       }
    ]
}