Initial commit: StackPilot Phase 1 (Core)

Self-hosted Docker Compose manager.
- Backend: FastAPI + docker-py + SQLite (JWT auth, file-first stacks,
  lifecycle, live status, WebSocket logs, docker-run converter, audit log)
- Frontend: React + Vite + Tailwind (login/setup, dashboard, stacks,
  stack detail, Monaco editor, dark/light theme)
- Deployment: docker-compose.yml, Dockerfiles, nginx reverse proxy

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/database.py

@@ -0,0 +1,31 @@
+"""SQLModel database setup."""
+from __future__ import annotations
+
+import os
+from collections.abc import Generator
+
+from sqlmodel import Session, SQLModel, create_engine
+
+from config import settings
+
+os.makedirs(settings.DATA_DIR, exist_ok=True)
+_DB_PATH = os.path.join(settings.DATA_DIR, "stackpilot.db")
+_DB_URL = f"sqlite:///{_DB_PATH}"
+
+engine = create_engine(
+    _DB_URL,
+    echo=False,
+    connect_args={"check_same_thread": False},
+)
+
+
+def init_db() -> None:
+    # Import models so they are registered on SQLModel.metadata.
+    import models  # noqa: F401
+
+    SQLModel.metadata.create_all(engine)
+
+
+def get_session() -> Generator[Session, None, None]:
+    with Session(engine) as session:
+        yield session