Outer hardening: AppArmor profile, pids limit, egress allowlist proxy

Inner codex sandbox stays danger-full-access by choice (bwrap
path is a separate decision); this hardens everything around it:
- DockerExecutor: --security-opt plumbing (repeatable, dedups
  no-new-privileges), --pids-limit (CLI default 512, fork-bomb
  guard), per-call extra_env (-e NAME=VALUE, non-secrets only,
  e.g. proxy URLs; the model key still goes by -e NAME only).
- Worker: --egress-proxy-port (0 = off). When on, Docker task
  containers get HTTP(S)_PROXY pointing at the host filtering
  proxy via their network gateway IP (tenant network gateway
  or default bridge gateway). Gateway unresolvable => the
  attempt fails instead of running unproxied (fail closed,
  same rule as tenant network creation failure).
- AppArmor profile deploy/apparmor/docker-codex: docker-default
  base + deny network raw/packet, deny ptrace, deny mount/
  umount/pivot_root, deny dangerous capabilities, deny writes
  to /proc/sys, /sys, /proc/keys. Deliberately NO userns rule
  (that would enable the bwrap path, not this one). File rules
  mirror docker-default (broad + sensitive denies); a strict
  file allowlist would need profiling codex's file access set
  and is not claimed here.
- Egress proxy deploy/egress/: Tinyproxy with
  FilterDefaultDeny + anchored domain allowlist (relay,
  github, pypi, npm). Anchoring matters: an unanchored
  'github.com' regex would also match 'evilgithub.com'.
- Seccomp honesty (README): Docker default seccomp already
  enforces on all task containers; no new stricter allowlist
  is claimed in this change (building one from memory risks
  silently breaking the toolchain; it needs syscall profiling
  first).
Tests: 3 outer-hardening tests (security-opt dedup, pids
limit, proxy env without leaking the key value, gateway
parse/fail, proxy fail-closed). Full suites pass.

deploy/autoscaler/codex-autoscaler.service

@@ -14,7 +14,7 @@ EnvironmentFile=/etc/codex-app-server/env
 # scaler 会按实例强制追加；--db 只给 scaler，scaler 会补给 worker。
 # 注意：启用 autoscaler 后必须停掉静态 codex-cloud-worker，
 # 否则两边同时派任务（scaler 只管理 autoscale-* 实例）。
-ExecStart=/usr/bin/python3 -m cloud.autoscaler --db /var/lib/codex-app-server/control.db --interval 30 --min-workers 1 --max-workers 2 --per-worker-capacity 2 --scale-down-after 3 --drain-timeout 60 --state-file /var/lib/codex-app-server/autoscaler-state.json --log-dir /var/lib/codex-app-server/autoscaler-logs -- --interval 10 --config /opt/codex-app-server/host-config-docker.json --executor docker --docker-image codex-app-server:latest --docker-user 1003:1004 --docker-cpus 2 --docker-memory 2g --docker-extra-mounts /opt/codex-app-server/work:/app/work,/var/lib/codex-app-server/codex-home:/var/lib/codex-app-server/codex-home,/var/lib/codex-app-server/repos:/var/lib/codex-app-server/repos,/var/lib/codex-app-server/test-repo:/var/lib/codex-app-server/test-repo --repos-dir /var/lib/codex-app-server/repos --tenant-isolation --tenants-root /var/lib/codex-app-server/tenants --tenant-template-home /var/lib/codex-app-server/codex-home --tenant-template-repo /var/lib/codex-app-server/test-repo
+ExecStart=/usr/bin/python3 -m cloud.autoscaler --db /var/lib/codex-app-server/control.db --interval 30 --min-workers 1 --max-workers 2 --per-worker-capacity 2 --scale-down-after 3 --drain-timeout 60 --state-file /var/lib/codex-app-server/autoscaler-state.json --log-dir /var/lib/codex-app-server/autoscaler-logs -- --interval 10 --config /opt/codex-app-server/host-config-docker.json --executor docker --docker-image codex-app-server:latest --docker-user 1003:1004 --docker-cpus 2 --docker-memory 2g --docker-extra-mounts /opt/codex-app-server/work:/app/work,/var/lib/codex-app-server/codex-home:/var/lib/codex-app-server/codex-home,/var/lib/codex-app-server/repos:/var/lib/codex-app-server/repos,/var/lib/codex-app-server/test-repo:/var/lib/codex-app-server/test-repo --repos-dir /var/lib/codex-app-server/repos --tenant-isolation --tenants-root /var/lib/codex-app-server/tenants --tenant-template-home /var/lib/codex-app-server/codex-home --tenant-template-repo /var/lib/codex-app-server/test-repo --docker-security-opt apparmor=docker-codex --docker-pids-limit 512 --egress-proxy-port 8888
 Restart=on-failure
 RestartSec=10
 # 停 scaler 时要等它把 worker 优雅排空（drain 60 秒 + 缓冲），