🐛 Create /config/env directory before services write into it 🐛

App-breaking bug found during full runtime verification of the act_runner
cache-server feature: `/config/env` was never explicitly created. It only
came into existence as a side effect of `__create_env_file()` copying
`/usr/local/etc/docker/env/default.sample` into it — but that sample file
does not exist in this image's rootfs, so `__create_env_file()` returns
early without creating the directory. `05-dockerd.sh` and
`zz-act_runner.sh` then failed writing `/config/env/docker.local.sh` and
`/config/env/act_runner.local.sh` directly, logging
`No such file or directory` (non-fatal, but a real bug).

- rootfs/usr/local/bin/entrypoint.sh: added
  `mkdir -p "/config/env" 2>/dev/null || true` alongside the other
  `/config/*` directory creation lines
- TODO.AI.md: logged the fix and the upstream-template-sync follow-up

Verified: full end-to-end run with `--privileged --cap-add CHOWN
--cap-add SYS_TIME --cap-add SYS_ADMIN` (per README) shows no more
"No such file or directory" errors, gitea starts on port 80, dockerd
starts, act_runner cache server logs "Cache server has been started and
is listening on 44015", and both configured runners register
successfully ("Runner registered successfully." x2, RUNNERS_START=2).
`runners-cache.yaml` is generated with real (non-REPLACE_) cache config
values.

rootfs/usr/local/bin/entrypoint.sh

@@ -240,6 +240,7 @@ mkdir -p "/data/logs" 2>/dev/null || true
 mkdir -p "/run/init.d" 2>/dev/null || true
 mkdir -p "/config/enable" 2>/dev/null || true
 mkdir -p "/config/secure" 2>/dev/null || true
+mkdir -p "/config/env" 2>/dev/null || true
 mkdir -p "/usr/local/etc/docker/exec" 2>/dev/null || true
 # - - - - - - - - - - - - - - - - - - - - - - - - -
 # create required files