feat: initial TrustOS platform scaffold

- FastAPI backend: auth, findings, dashboard, attack paths, footprint, AI translator, risk calculator, PDF report generator
- Next.js frontend: Vault dashboard, login, findings table, finding detail with AI coach, digital footprint, reports
- PostgreSQL data model: tenants, users, assets, findings, risk scores, audit reports, attack paths
- Docker Compose + Dockerfiles for all services
- Demo seed data: Acme Corp with 6 findings and 90-day risk score history
- AI Risk Translator (OpenAI/Anthropic) with plain-English business impact
- Role-based access: executive / it_admin / trustos_admin
- Scope-lock engine: authorization required before any assessment

Stage 1-8 complete: Phase 1 Vault Audit product ready

backend/app/db/session.py

@@ -0,0 +1,27 @@
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine, async_sessionmaker
+from sqlalchemy.orm import DeclarativeBase
+from app.core.config import settings
+
+engine = create_async_engine(
+    settings.DATABASE_URL,
+    echo=False,
+    pool_pre_ping=True,
+    pool_size=10,
+    max_overflow=20,
+)
+
+AsyncSessionLocal = async_sessionmaker(
+    engine, class_=AsyncSession, expire_on_commit=False
+)
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+async def get_db() -> AsyncSession:
+    async with AsyncSessionLocal() as session:
+        try:
+            yield session
+        finally:
+            await session.close()