base-trixie: the image on Debian trixie, Postfix 3.10.13; Received: hidden on 465/587

The runtime base is debian:trixie-slim, the build stage golang:1.26-trixie:
Postfix 3.10.13 with upstream's 2026 security fixes up to the August
batch, libmilter 8.18.1, OpenSSL 3.5. Every citation of another program in
code, scripts and documents was re-read against the trixie sources
(dev/upstream; bookworm's kept in dev/upstream-bookworm) and updated;
development.md's cited-package table holds the trixie versions.

What the re-reading changed in behaviour:
- logtail: reject lines with sasl_method/sasl_username/sasl_sender
  (smtpd_check.c:1019-1026); cleanup's "removed (canceled)" forgets a
  port-25 id (cleanup_api.c:363-364).
- internal/postfix/retry.go reads postconf's stdout only: since 3.9 a
  deprecated-parameter warning on stderr made one value too many and the
  panel fell back to the compiled-in retry policy.
- logrotate-loop.sh: logrotate 3.22 exits 1 when it ignores a config;
  the loop refuses on that output whatever the status.
- postfix-config.sh: cyrus_sasl_config_path set explicitly (bookworm's
  07_sasl_config.diff is gone); maillog_file_permissions=0640; mynetworks
  explicit; Dockerfile: SYNC_CHROOT= in /etc/default/postfix,
  opendkim-tools dropped, openssl named, systemd-standalone-sysusers so
  cron does not bring the whole of systemd.
- The selfpost group is 10998, outside the system range 100-999: in
  trixie a package took 998 and the build failed (owner's decision:
  a conflict-free id, the distribution's own ids untouched). The
  entrypoint hands /data back by name when the user or the group differs.
  Guide, backup refusal text, help (design commit 68ec8b2), e2e.
- smtpd_hide_client_session=yes on smtps and submission (owner's
  decision): Received: names no client, TLS, login or protocol; port 25
  keeps the full header. e2e checks both.
- test/upstream/opendkim-probe.sh makes keys with openssl genrsa.

Tests: on the server, make e2e exit 0 (674 s, the image built on trixie),
go vet + go test 27 packages ok. CHANGELOG [Unreleased], guide,
architecture.md, security.md, roadmap.

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

test/e2e/restore_test.go

@@ -24,7 +24,7 @@ import (
 // record that was published before the backup.
 func testFullBackupRestore(t *testing.T, sc *scenario) {
 	// A private key the panel may not read - the state a server is in until
-	// its operator gives the key to group 998. The panel does not make an
+	// its operator gives the key to group 10998. The panel does not make an
 	// archive without it: it refuses, names the file and says what to do.
 	keyPath := filepath.Join(h.stageDir, "certs", "privkey.pem")
 	if err := os.Chmod(keyPath, 0o600); err != nil {
@@ -34,7 +34,7 @@ func testFullBackupRestore(t *testing.T, sc *scenario) {
 	if err != nil {
 		t.Fatalf("full backup with an unreadable key: %v", err)
 	}
-	if resp.StatusCode != 500 || !strings.Contains(body, "not allowed to read certs/privkey.pem") || !strings.Contains(body, "chgrp 998") {
+	if resp.StatusCode != 500 || !strings.Contains(body, "not allowed to read certs/privkey.pem") || !strings.Contains(body, "chgrp 10998") {
 		t.Fatalf("full backup with an unreadable key: status %d, want a refusal that names the file and the way out:\n%.800s", resp.StatusCode, body)
 	}
 	if err := os.Chmod(keyPath, 0o644); err != nil {