fix(CPL-300): drop root in lit-api-server and lit-actions containers

[GTC6244]

Summary

Closes the defense-in-depth gap from CPL-300 (audit finding from .context/CSO-CPL-281-report.md#11). Both Dockerfiles previously had no USER directive, so the containers ran as root inside the Phala CVM. Any RCE in lit-api-server (sandbox escape, panic-handler exploit, etc.) would have inherited root with full access to /var/run/dstack.sock — turning the dstack KMS into a signing/attestation oracle for arbitrary report_data.

Both Dockerfiles now drop to a non-root lit user (uid 10001, matching the existing convention in Dockerfile.otel-collector:9):

• Dockerfile.lit-api-server: useradd -u 10001 -m lit + USER lit before CMD
• Dockerfile.lit-actions: same pattern

Why this works without compose changes

• /tmp/lit_actions.sock — lit-actions/grpc/unix.rs:66 already chmods the bound socket to 0o777, so the lit-api-server side connects regardless of UID. The shared lit-socket named volume initialises from the image's /tmp (mode 1777), so non-root binds.
• /var/run/dstack.sock — bind-mounted from the host; the same compose's dstack-ingress service already accesses this socket without privileged mode, confirming non-root works.

Verification

• docker buildx build --check — passes both Dockerfiles, no warnings.
• Live container check: useradd -u 10001 -m lit succeeds in debian:bookworm-slim, /tmp is mode 1777 (drwxrwxrwt), the lit user can create files there. So lit-actions can bind /tmp/lit_actions.sock.

Out of scope

The unrelated root-level Dockerfile (development convenience build) is also missing a USER directive but is not deployed to Phala. Tracked separately if the audit decides to widen scope.

Test plan

• Phala Simulator Validation CI passes (validates dstack socket access end-to-end).
• After merge: trigger Phala deploy on next and confirm lit-api-server and lit_actions start, id shows uid=10001(lit), and /attestation endpoint still returns a valid quote.

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR hardens the deployed Phala CVM containers by ensuring lit-api-server and lit-actions no longer run as root, reducing blast radius if an RCE or sandbox escape occurs.

Changes:

• Add a dedicated non-root lit user (UID 10001) to the lit-api-server runtime image and switch execution to that user.
• Add the same non-root lit user (UID 10001) to the lit-actions runtime image and switch execution to that user.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Dockerfile.lit-api-server	Creates non-root lit user (uid 10001) and sets USER lit before starting lit-api-server.
Dockerfile.lit-actions	Creates non-root lit user (uid 10001) and sets USER lit before starting lit_actions.

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