feat(docker): guide clone installation and validate paired update artifacts

scripts/docker-install.sh

@@ -42,7 +42,8 @@ printf '%s\n' 'EpicNext-Cms installation' 'Requires an existing Habbo database a
 read_value 'Public CMS URL (e.g. https://hotel.example)' "${CMS_PUBLIC_URL:-}"
 public_url="${REPLY%/}"
 http_url "$public_url" && [[ "$public_url" != *'?'* ]] || fail "Enter an HTTP(S) URL without credentials, query or fragment."
-read_value 'Delivery method: prebuilt or source' "${CMS_INSTALL_MODE:-prebuilt}"
+printf '%s\n' 'Source builds need repository access and public build dependencies. Prebuilt images additionally need registry package access (docker login on this host for private packages).'
+read_value 'Delivery method: prebuilt or source' "${CMS_INSTALL_MODE:-source}"
 mode="$REPLY"
 [[ "$mode" = prebuilt || "$mode" = source ]] || fail "Choose prebuilt or source."
 if [[ "$mode" = prebuilt ]]; then