Fix lab automation: 8 bugs blocking make lab-up + verified C2 boot

[AndrewAltimit]

Summary

Audit of the Makefile, requirements files, CI, and lab images turned up eight bugs that prevented a clean checkout from booting the lab. All are fixed and verified end-to-end by building images and hitting the C2 operator API from the host.

• tools/idol/01-credential-harvest.py:134 — NameError: name 'targets' is not defined. Extracted _credential_targets() helper. Hidden because tools/idol/tests/ was not wired into CI; now it is.
• 5 mock-* Dockerfiles (mock-imds, mock-entra, mock-slack, mock-oauth, mock-graph) COPYed requirements.txt files deleted in the uv-workspace migration (commit 1bdeeeb). Replaced with inline pip install matching the existing Dockerfile.beacon / Dockerfile.c2-server pattern.
• Dockerfile.c2-server and Dockerfile.exploit-server — useradd operator failed because python:*-slim has the Debian-legacy operator:x:37 system group. Use -g operator operator to reuse it.
• Dockerfile.c2-server missing deps — tools/c2/server.py imports cryptography and pyjwt; only flask requests was installed.
• ContainmentGuard.assert_loopback rejected 0.0.0.0, blocking the server from binding inside the container. Now allowed only when in_docker() is true; host port mapping remains loopback-only.
• docker-compose.lab.yml declared internal: true and ports: on every service — Docker silently drops the publication. Added a lab-bridge network for user-facing services; beacons stay on lab-internal only. ContainmentGuard continues enforcing loopback/RFC1918 at the tool layer.
• make lab-arc-up / lab-arc-down referenced infra/lab/mock-imds/Dockerfile and mock_imds.py, neither of which exists. The existing mock-imds server already serves the Azure Arc MSI endpoint unconditionally — target now just ensures the compose service is up.
• 6 ci/check_*.py gates were advertised in tool READMEs as CI gates but never invoked by either workflow. Wired all six into the Repo hygiene step.

While here: bumped python:3.12-slim to python:3.14-slim across the 9 Dockerfiles and the phishing compose fragment.

Test plan

• Branched off main, no merge conflicts
• uv sync --all-packages clean
• All 9 hygiene checks pass (tools/ci/check_*.py and ci/check_*.py)
• pytest — 108 passed, 3 skipped (was 44; tools/idol/tests/ adds 64)
• Rust workspace builds + all tests pass (cargo test --workspace -- --test-threads=1)
• Dashboard builds (reports/databricks-apps-assessment/build.py)
• All Dockerfiles build cleanly (docker compose build)
• docker compose up -d c2-server publishes 127.0.0.1:8443->8443/tcp
• curl http://127.0.0.1:8443/api/status from host returns HTTP 401 {"error":"unauthorized"} (AuthGuard correctly rejecting unauthenticated call)
• CI run on this branch is green

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