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/models/audit_log.py

@@ -0,0 +1,23 @@
+"""Immutable audit trail model."""
+
+from datetime import UTC, datetime
+
+from sqlalchemy import DateTime, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.database import Base
+
+
+class AuditLog(Base):
+    __tablename__ = "audit_logs"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    timestamp: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), default=lambda: datetime.now(UTC), index=True
+    )
+    username: Mapped[str] = mapped_column(String(255), index=True)
+    action: Mapped[str] = mapped_column(String(100), index=True)  # e.g. server.create
+    target: Mapped[str | None] = mapped_column(String(255), nullable=True)  # e.g. server name
+    result: Mapped[str] = mapped_column(String(50), default="success")  # success | failure
+    details: Mapped[str | None] = mapped_column(Text, nullable=True)  # JSON blob
+    ip_address: Mapped[str | None] = mapped_column(String(45), nullable=True)