P3-1: database.py 统一使用 config.py 中的 Settings，消除配置重复定义

apps/api/app/core/database.py

@@ -1,34 +1,12 @@
-import os
-from typing import Optional
+"""
+数据库连接管理
 
-from pydantic_settings import BaseSettings, SettingsConfigDict
+P3-1 Fix: 统一使用 config.py 中的 Settings 类，消除配置重复定义。
+"""
+
+from app.config import settings
+from packages.adapters.sqlalchemy_impl.session import build_session_factory
 
 
-class DatabaseSettings(BaseSettings):
-    database_url: str = "postgresql+psycopg://postgres:postgres@postgres:5432/xiaoxia_saas"
-    pool_size: int = 20
-    max_overflow: int = 40
-    pool_timeout: int = 30
-    pool_recycle: int = 3600
-
-    model_config = SettingsConfigDict(
-        env_file=".env",
-        env_file_encoding="utf-8",
-        case_sensitive=False,
-        extra="ignore",
-    )
-
-
-_settings: Optional[DatabaseSettings] = None
-
-
-def get_database_settings() -> DatabaseSettings:
-    global _settings
-    if _settings is None:
-        env = os.getenv("APP_ENV", "development")
-        env_file = f".env.{env}" if env != "development" else ".env"
-        if os.path.exists(env_file):
-            _settings = DatabaseSettings(_env_file=env_file)
-        else:
-            _settings = DatabaseSettings()
-    return _settings
+# P3-1 Fix: 直接使用 settings 中的配置，而不是重复定义
+_engine, _SessionLocal = build_session_factory(settings.DATABASE_URL)