refactor: 简化WorkerConfig配置

移除显式的env_file配置，依赖pydantic-settings默认行为自动读取.env文件

src/BowongModalFunctions/models/settings/cluster.py

@@ -36,8 +36,6 @@ class WorkerConfig(BaseSettings):
     cf_kv_namespace_id: Optional[str] = Field(default=None, description="Cloudflare KV Namespace ID")
 
     model_config = SettingsConfigDict(
-        env_file=".env",
-        env_file_encoding="utf-8",
         json_schema_extra={
             "description": "可通过本地环境变量加载对应Field, 不区分大小写, Modal创建App的Image时可通过dotenv加载指定.env文件写入到Docker Image的系统变量",
         }