Check in scripts/configs, organized and documented by host OS

Every script/config built this session (sanity-check, attacker-check,
the Gitea backup pipeline on both ends) now lives in this repo as
reference copies, not just described in prose - previously they only
existed on the live servers.

Split into scripts/alpha/ (Ubuntu 24.04.4 LTS) and
scripts/clients/vlda-01/ (Unraid 7.3.2), each with its own README
stating the exact OS/kernel and a file-by-file map to deployed paths,
since a script written for one host's conventions doesn't just work
unchanged on the other - the vlda-01 README in particular documents
the persistence gotchas that actually broke earlier attempts (RAM-
backed root filesystem, VFAT /boot with no execute bit, Unassigned
Device auto-mount). Root README.md now links directly to these files
from each relevant section instead of only describing them.

Explicitly not included: the dedicated SSH private key vlda-01 uses to
authenticate to alpha - noted in clients/vlda-01/README.md to
regenerate rather than ever commit one.

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

scripts/alpha/sanity-check.service

@@ -0,0 +1,13 @@
+[Unit]
+Description=Post-boot sanity check for alpha.jayfield.org
+After=network-online.target named.service mariadb.service postfix@-.service dovecot.service fail2ban.service apache2.service docker.service rspamd.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStartPre=/bin/sleep 10
+ExecStart=/usr/local/sbin/sanity-check.sh
+RemainAfterExit=yes
+
+[Install]
+WantedBy=multi-user.target