feat(delivery): add Ansible playbook for native MySQL provisioning

Add mysql-deploy.yml playbook for bare-metal MySQL 8.0 delivery via
AWX: parameter validation, resource preflight checks, apt install,
AppArmor adaptation, per-instance directory layout, Jinja2 config
template (buffer pool sizing, binlog, GTID), systemd template unit
(mysql-delivery@.service), admin account setup, and TCP health
verification. Includes example inventory.

Relates-to: #97

ansible/files/mysql-delivery@.service

@@ -0,0 +1,20 @@
+[Unit]
+Description=XINFRA MySQL delivery instance %i
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=notify
+User=mysql
+Group=mysql
+RuntimeDirectory=mysql-delivery-%i
+RuntimeDirectoryMode=0755
+ExecStart=/usr/sbin/mysqld --defaults-file=/etc/mysql/mysql-delivery/%i.cnf
+Restart=on-failure
+RestartSec=5s
+TimeoutStartSec=120s
+LimitNOFILE=65535
+OOMScoreAdjust=-200
+
+[Install]
+WantedBy=multi-user.target