feat: add local docker dev stack

[sidpalas]

• add a local Docker Compose development stack for web, control-plane, and a minimal Docker-backed sandbox provider
• implement a docker sandbox backend plus a small docker-sandbox-api service to create, stop, and reap local sandbox containers
• improve local-dev reliability with D1 migration bootstrapping, provider env passthrough, socket/auth UX fixes, and cleanup/reset scripts for local sandbox state

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Note: because cloudflare is the production deployment target, there isn't too much value in containerizing the services for development purposes (and here the containers are mostly just wrapping the run dev commands). It does make the networking between sandbox container and control plane slightly simpler, but dunno if it is worth the additional tooling (esspecially for folks less familiar with docker/containers)