fix: 修改LLMProvider 类型

ai_service/llm/enums.py

@@ -0,0 +1,32 @@
+from enum import Enum
+
+
+class LLMProvider(str, Enum):
+    """LLM 提供商枚举"""
+    DEEPSEEK = "deepseek"
+    TONGYI = "tongyi"
+    OPENAI = "openai"
+    GOOGLE_GENAI = "google-genai"
+    
+    @classmethod
+    def get_model_by_platform(cls, platform: str) -> tuple[str, str]:
+        """根据平台名称获取对应的模型和API密钥环境变量名"""
+        if platform == cls.TONGYI:
+            return 'qwen-plus', 'DASHSCOPE_API_KEY'
+        elif platform == cls.DEEPSEEK:
+            return 'deepseek-chat', 'DEEPSEEK_API_KEY'
+        elif platform == cls.OPENAI:
+            return 'gpt-3.5-turbo', 'OPENAI_API_KEY'
+        elif platform == cls.GOOGLE_GENAI:
+            return 'gemini-pro', 'GOOGLE_API_KEY'
+        else:
+            # 默认使用 DeepSeek
+            return 'deepseek-chat', 'DEEPSEEK_API_KEY'
+    
+    @classmethod
+    def from_string(cls, platform: str) -> 'LLMProvider':
+        """从字符串创建枚举值，如果不存在则返回默认值"""
+        try:
+            return cls(platform)
+        except ValueError:
+            return cls.DEEPSEEK  # 默认返回 DeepSeek