Deploy a fresh Stalwart and ihasmail, linked, in one command

deploy stands up Stalwart 0.16, ihasmail and (for a mail host) Caddy as a
compose project: completes Stalwart's bootstrap over x:Bootstrap, links
ihasmail over the private network, requests certificates for both Caddy
(TLS-ALPN-01) and Stalwart (HTTP-01 through Caddy), makes the auto-ban safe
behind the proxy, and proves the link by signing in through the webmail.
--local gives a loopback-only pair. certs retries Stalwart's certificate;
destroy removes a deployment.

e2e/public.sh runs the whole mail-host path against Pebble with no
internet involved.

.gitignore

@@ -0,0 +1,17 @@
+# Binaries
+/bin/
+/dist/
+/ihasmail-oneshot
+
+# Test / coverage
+*.out
+*.test
+
+# A deployment directory written by a local run: it holds secrets.
+/ihasmail-*/
+/e2e/work/
+
+# Editor / OS
+.DS_Store
+.idea/
+.vscode/