Phase 10: deployment (Apache compose + proxy fragments, CI release) + docs

- deploy/docker-compose.yml: pinned-tag ghcr image, hardened (cap_drop ALL +
  minimal cap_add, no-new-privileges, panel bound to 127.0.0.1 only). Apache
  itself runs on the host (spec 10.5), fragment at deploy/apache/.
- Alternative reverse-proxy fragments: nginx (+certbot sidecar), Caddy
  (automatic ACME), Traefik (+acme.json PEM extraction script).
- .github/workflows/release.yml: tag-triggered ghcr.io publish, version piped
  from the git tag into both the binary ldflags and the image tag (spec 10.1).
- Closed a gap from Phase 1: logrotate was installed but never invoked;
  wired up build/logrotate-mail.conf + logrotate-loop.sh + a supervisor
  program (copytruncate, since postlogd holds mail.log open with nothing to
  signal on rotation).
- README rewritten: site requirements checklist, reverse-proxy comparison,
  DNS setup (server- vs domain-level), IP warmup, backup/restore vs domain
  export/import, fixed-tag rationale, machine requirements.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

build/supervisord.conf

@@ -103,6 +103,20 @@ stdout_logfile_maxbytes=0
 stderr_logfile=/dev/stderr
 stderr_logfile_maxbytes=0
 
+; Periodic logrotate for /var/log/mail.log (spec 9, 10: daily, 7-14 files kept
+; in the image). Runs as root so logrotate can read/rotate the log; never exits
+; non-zero, so it neither trips the crashexit listener nor needs restarting.
+[program:logrotate]
+command=/usr/local/bin/logrotate-loop.sh
+priority=400
+autostart=true
+autorestart=true
+startsecs=0
+stdout_logfile=/dev/stdout
+stdout_logfile_maxbytes=0
+stderr_logfile=/dev/stderr
+stderr_logfile_maxbytes=0
+
 [eventlistener:crashexit]
 command=/usr/local/bin/crashexit.py
 events=PROCESS_STATE_FATAL