Remove obsolete port-binding rewrite from brev/dev-start.bash

[robobryce]

Problem

PR #208 changed the tutorial Compose files so their published services bind directly to 0.0.0.0. brev/dev-start.bash still creates /tmp/docker-compose.<tutorial>.dev.yml and runs sed to rewrite 127.0.0.1 to 0.0.0.0 before every start. That rewrite is now a no-op and the temporary file obscures the Compose file actually being run.

Proposed change

Remove DOCKER_COMPOSE_DEV and the sed rewrite, and run Compose against the prepared tutorial Compose file directly. Preserve the existing warning filtering.

Acceptance criteria

• dev-start.bash works with --mount and --no-mount.
• Jupyter and Nsight services remain reachable externally.
• No temporary Compose file is created only to rewrite host bindings.

Follow-up to #208.