feat: add Docker setup for RouterOS and Mailpit services

lab/README.md

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+# Local RouterOS test lab
+
+This lab runs MikroTik RouterOS CHR for development and manual tests.
+
+## Start the lab
+
+```sh
+make start
+make state
+```
+
+RouterOS can take up to two minutes to accept SSH connections on its first boot.
+The `routeros-init` container retries during that period and exits after it applies the mail settings.
+
+## Access
+
+| Service | Address |
+| --- | --- |
+| Mailpit web interface | <http://localhost:8025> |
+| RouterOS WebFig | <http://localhost:12280> |
+| RouterOS WinBox | `localhost:18291` |
+| RouterOS SSH | `localhost:12222` |
+| RouterOS Telnet | `localhost:12223` |
+| RouterOS API | `localhost:18728` |
+| RouterOS API over TLS | `localhost:18729` |
+
+!! Use the RouterOS user `admin` with an empty password. Use this account inside the isolated lab.
+
+## Mailpit and ping
+
+Expect `ping mailpit` from RouterOS to time out. Docker DNS still resolves the `mailpit` name, and SMTP traffic can reach port `1025`.
+The Docker and QEMU network path does not provide a useful ICMP health check for this service.
+
+Test SMTP from a RouterOS terminal:
+
+```routeros
+/tool e-mail send to="lab@example.test" subject="lab test" body="mail works"
+```
+
+Open <http://localhost:8025> and check that Mailpit received the message. Use message delivery as the health check for this lab.
+
+## Usage
+
+```routeros
+/system script run BackupAndUpdate
+```
+
+Follow the script log while it runs:
+```routeros
+/log print follow where message~"Bkp&Upd"
+```