```

refactor(core): 重构核心模块结构并更新导入路径

- 将配置相关的设置从 app.core.config 移除
- 将常量定义从 app.core.constants 移除
- 将数据库相关功能从 app.core.database 移除
- 将基础数据库模型从 app.core.db_base 移除
- 将敏感信息掩码功能从 app.core.masking 移除
- 将中间件定义从 app.core.middleware 移除
- 将操作保护功能从 app.core.operation_guard 移除
- 将分页工具从 app.core.pagination 移除
- 将请求上下文管理从 app.core.request_context 移除
- 将调度器功能从 app.core.scheduler 移除
- 将安全认证逻辑从 app.core.security 移除
- 将任务队列相关功能从 app.core.task_queue 移除
- 将时间工具从 app.core.time 移除
- 更新 alembic 配置中的 Base 模型导入路径
- 更新各模块中对重构后组件的引用路径
```

app/core/database/__init__.py

@@ -0,0 +1,30 @@
+from typing import Any
+
+from app.core.database.base import Base
+
+__all__ = [
+    "Base",
+    "LegacySessionLocal",
+    "SessionLocal",
+    "engine",
+    "get_db",
+    "get_legacy_db",
+    "legacy_engine",
+]
+
+_SESSION_EXPORTS = {
+    "LegacySessionLocal",
+    "SessionLocal",
+    "engine",
+    "get_db",
+    "get_legacy_db",
+    "legacy_engine",
+}
+
+
+def __getattr__(name: str) -> Any:
+    if name in _SESSION_EXPORTS:
+        from app.core.database import session
+
+        return getattr(session, name)
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")

app/core/database/base.py

@@ -0,0 +1,7 @@
+from sqlalchemy.orm import DeclarativeBase
+
+
+class Base(DeclarativeBase):
+    """Base class for SQLAlchemy ORM models."""
+
+    pass

app/core/database/session.py

@@ -0,0 +1,57 @@
+from collections.abc import Generator
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import Session, sessionmaker
+
+from app.core.config import get_settings
+
+from .base import Base
+
+
+settings = get_settings()
+
+engine = create_engine(settings.database_url, pool_pre_ping=True, pool_recycle=3600)
+SessionLocal = sessionmaker(bind=engine, autoflush=False, autocommit=False, expire_on_commit=False)
+
+legacy_engine = (
+    create_engine(settings.legacy_database_url, pool_pre_ping=True, pool_recycle=3600)
+    if settings.legacy_database_url
+    else None
+)
+LegacySessionLocal = (
+    sessionmaker(bind=legacy_engine, autoflush=False, autocommit=False, expire_on_commit=False)
+    if legacy_engine
+    else None
+)
+
+__all__ = [
+    "Base",
+    "LegacySessionLocal",
+    "SessionLocal",
+    "engine",
+    "get_db",
+    "get_legacy_db",
+    "legacy_engine",
+]
+
+
+def get_db() -> Generator[Session, None, None]:
+    """Yield an application database session for FastAPI dependencies."""
+
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
+
+
+def get_legacy_db() -> Generator[Session, None, None]:
+    """Yield a legacy database session when the legacy connection is configured."""
+
+    if LegacySessionLocal is None:
+        raise RuntimeError("LEGACY_DATABASE_URL is not configured")
+    db = LegacySessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()