fix: build Caddy with CF plugin from source (ARM64 compat)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/deploy/docker/Dockerfile.caddy

@@ -0,0 +1,9 @@
+# Caddy with Cloudflare DNS plugin — builds for any arch
+FROM caddy:2-builder AS builder
+
+RUN xcaddy build \
+    --with github.com/caddy-dns/cloudflare
+
+FROM caddy:2
+
+COPY --from=builder /usr/bin/caddy /usr/bin/caddy