add multi-arch docker installer

deploy/arm64-installer/.env.example

@@ -1,8 +1,14 @@
-# ours RP ARM64 installer configuration
+# ours RP Docker installer configuration
+# `build_docker_installer_package.sh` rewrites package-specific defaults below.
 # 中文说明见 docs/README.zh-CN.md。English guide: docs/README.en.md
 
+# Package metadata and architecture guardrails.
+PACKAGE_ARCH=arm64
+PACKAGE_PLATFORM=linux/arm64
+ALLOW_CROSS_ARCH=0
+
 # Compose project name.
-COMPOSE_PROJECT_NAME=ours-rp-arm64
+COMPOSE_PROJECT_NAME=ours-rp-arm64-installer
 
 # Runtime image loaded from images/*.tar.gz by install.sh.
 RPKI_IMAGE=ours-rp-runtime-arm64:dev
@@ -13,7 +19,7 @@ RPKI_PLATFORM=linux/arm64
 SOAK_RESTART_POLICY=unless-stopped
 
 # Host-side persistent data directory. All state/runs/logs/monitoring data are bind-mounted here.
-HOST_DATA_DIR=/var/lib/ours-rp-arm64
+HOST_DATA_DIR=/var/lib/ours-rp-arm64-installer
 
 # RIR list. Options: afrinic,apnic,arin,lacnic,ripe
 RIRS=afrinic,apnic,arin,lacnic,ripe
@@ -72,7 +78,7 @@ METRICS_PORT=9556
 METRICS_POLL_SECS=10
 
 # Prometheus / Grafana.
-# Monitor images are packaged as ARM64 docker-save archives and loaded by install.sh.
+# Monitor images are packaged as docker-save archives and loaded by install.sh.
 MONITOR_PLATFORM=linux/arm64
 PROMETHEUS_IMAGE=prom/prometheus:v2.55.1
 GRAFANA_IMAGE=grafana/grafana:11.3.1