certbot: certs/ links into /etc/letsencrypt, mounted at the same path; the backup follows them

C-A1, C-Q4, D-guide:258, :291, :722. certbot's live/<host>/*.pem are
relative links into ../../archive/<host>/ (eff-certbot docs, "Where are
my certificates?": point a server at them "or create symlinks"). The
guide had `ln -s /etc/letsencrypt/live/<host> certs` and the nginx
fragment mounted live/<host> alone: inside the container the links led
into a directory it did not have - postfix-config.sh's [ -f ] false, no
copy, Postfix without a certificate - and the panel's backup, reading
certs/ through /selfpost-deploy, skipped links silently.

Now certs/fullchain.pem and certs/privkey.pem are links to
/etc/letsencrypt/live/<host>/, and /etc/letsencrypt is mounted read-only
at the same path: a commented line in deploy/docker-compose.yml for the
Apache scenario, mounted in the nginx fragment (./nginx/certbot-etc). The
guide's steps add certbot's own commands for a server that is not root -
chmod 0755 live archive, chgrp 998 + chmod 0640 the key, which certbot
keeps on renewal - so the panel reads them (Health, backup). Postfix's
side follows links already ([ -f ], cp, cmp, openssl). The vhost comment
says the same. The backup table: links are followed by the panel's
backup; a stopped tar stores them as links unless -h (GNU tar).

internal/backup: addTree follows, for certs/ only, a link to a regular
file and archives that file under the link's name; a link to nothing
reachable is an error naming it and the mount.

Tests: TestCertsLinksAreFollowed (certs/ -> live/ -> archive/, the
archive holds the files; the tree gone, Check names the dangling link;
Linux). Stand (2026-10-15, make e2e, exit 0): the stand mounts
./letsencrypt at /etc/letsencrypt; new certbot_layout_followed puts a new
pair into letsencrypt/archive/, relative links in live/, absolute links
in certs/, recreates the container: 465 serves the new serial, Health
names no renewal waiting, and the full backup holds certs/*.pem as
regular files with the archive's bytes. go vet and go test ./... pass on
the server (24 packages); the Linux-only tests of this session run there
and pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/audit-2026-10-12.md

@@ -1005,12 +1005,16 @@ those after it move up one patch number each.
    it; a test with two concurrent opens behind a held lock. - **Opus**
    *Done 2026-10-15:* the test fails without the fix exactly as the
    register said ("table settings already exists") and passes with it.
-- [ ] **Certificates from certbot** (C-A1, C-Q4, D-guide:258, :291, :722):
+- [x] **Certificates from certbot** (C-A1, C-Q4, D-guide:258, :291, :722):
    certbot's `live/` files are relative links into `archive/`, so mounting
    `live/<host>` alone, or linking `certs` to it, leaves Postfix without a
    certificate and the backup without it. The deploy fragments mount
    `/etc/letsencrypt` read-only and point the paths into it; the backup
    follows a link under `certs/` to a regular file. - **Opus**
+   *Done 2026-10-15:* `certs/` holds links into `/etc/letsencrypt/live/`,
+   mounted read-only at the same path; certbot's own `chmod 0755` and
+   `chgrp`/`chmod 0640` for a server that is not root (kept on renewal) let the
+   panel read them; no copying hook.
 - [ ] **The rest of what the sources contradict** (C-M7 `<pct>0</pct>`,
    C-E2 the e2e zone serial, C-D1 a release gate comparing the image's
    package versions with the ones cited, C-K8/K9 and the comments the