Harden the Docker images by dropping root privileges, and make the
bind-mount workflow less fiddly.
- Create a non-root `app` user (uid/gid 1000) in both images and add
`USER app` before the entrypoint, so ocrmypdf (and the
webservice/watcher) no longer run as root. This also fixes the
previously dangling `--chown=app:app`, which referenced a user that
was never created. The Ubuntu base ships a default `ubuntu`/1000 user,
so remove it first so `app` can take uid 1000 (parity with Alpine).
- Add `WORKDIR /data` (created and app-owned) so bind-mounted input and
output can be passed as relative paths without `--workdir`. The
webservice/watcher are now invoked by absolute path (`/app/*.py`)
since the working directory is no longer `/app`.
- Drop the redundant `ppa:alex-p/tesseract-ocr5` from the Ubuntu image:
Tesseract 5 ships in the Ubuntu archive as of 24.04, and the PPA had
no build for the 26.04 base, which broke the build outright.
- Rewrite docs/docker.md rootless-first: stdin/stdout piping as the
recommended permission-free path, then per-runtime volume guidance
(rootless Docker `--user 0:0`, Podman `--userns keep-id`, rootful
Docker as the special case). Update batch.md and the compose example
to match (absolute script paths, per-runtime `user:` guidance).
James R. Barlow
ff45e54c07