Initial scaffold: FastAPI backend + Vue 3 frontend + Docker setup

Backend: config/db/security/logging core, SQLAlchemy models (Server,
Credential, UpdateJob, UpdateLog, AuditLog, User), services (winrm, ssh,
cau, audit, job_runner), REST API (auth, servers, updates, audit),
Socket.io WebSocket layer.
Frontend: Vue 3 + TS + Pinia + Tailwind, Views (Dashboard, Servers,
Updates, Audit, Login), axios + socket.io-client, nginx prod config.

backend/app/core/database.py

@@ -0,0 +1,47 @@
+"""Database setup: async engine, session factory, declarative base."""
+
+from collections.abc import AsyncGenerator
+
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+from sqlalchemy.orm import DeclarativeBase
+
+from app.core.config import get_settings
+
+settings = get_settings()
+
+engine = create_async_engine(
+    settings.database_url,
+    echo=settings.log_level.upper() == "DEBUG",
+    pool_pre_ping=True,
+)
+
+async_session_factory = async_sessionmaker(
+    engine,
+    class_=AsyncSession,
+    expire_on_commit=False,
+    autoflush=False,
+)
+
+
+class Base(DeclarativeBase):
+    """Declarative base for all ORM models."""
+
+
+async def get_db() -> AsyncGenerator[AsyncSession, None]:
+    """FastAPI dependency yielding an async DB session."""
+    async with async_session_factory() as session:
+        try:
+            yield session
+            await session.commit()
+        except Exception:
+            await session.rollback()
+            raise
+
+
+async def init_db() -> None:
+    """Create all tables (scaffold mode; Alembic migrations come later)."""
+    # Import models so they register on the metadata
+    from app import models  # noqa: F401
+
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)