feat: complete leave approval MVP

ai-service/app/config.py

@@ -0,0 +1,17 @@
+from functools import lru_cache
+
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+
+class Settings(BaseSettings):
+    model_config = SettingsConfigDict(env_file=".env", extra="ignore")
+
+    qwen_api_key: str = ""
+    qwen_base_url: str = "https://dashscope.aliyuncs.com/compatible-mode/v1"
+    qwen_model: str = "qwen-plus"
+    request_timeout_seconds: float = 20.0
+
+
+@lru_cache
+def get_settings() -> Settings:
+    return Settings()