feat: Add FastAPI s6 sidecar PoC

- Sidecar DragonflyDB as Redis replacement
- Run pytheus in multiprocessing mode with Redis backend

s6/run_dragonfly

@@ -0,0 +1,3 @@
+#!/command/execlineb -P
+dragonfly --logtostderr --bind localhost --port 6379
+

s6/run_fastapi

@@ -0,0 +1,3 @@
+#!/command/execlineb -P
+ /bin/sh -c "cd /code && gunicorn app.main:app --workers 2 --worker-class uvicorn.workers.UvicornWorker --bind 0.0.0.0:80"
+