feat: add runnable simulator foundation

app/dependencies.py

@@ -0,0 +1,14 @@
+"""FastAPI dependency adapters."""
+
+from __future__ import annotations
+
+from fastapi import Request
+
+from app.db.pool import Database
+
+
+def get_database(request: Request) -> Database:
+    """Resolve the lifespan-owned database from application state."""
+
+    database: Database = request.app.state.database
+    return database