Pass Grafana env vars to Caddy container, fix Loki compactor config

- Add DOMAIN, GRAFANA_USER, GRAFANA_PASSWORD_HASH as environment vars
  on the Caddy container so Caddyfile can reference them
- Fix Loki compactor: add delete_request_store required when retention is enabled

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

infrastructure/docker-compose.yml

@@ -6,6 +6,10 @@ services:
       - "80:80"
       - "443:443"
       - "443:443/udp"
+    environment:
+      DOMAIN: ${DOMAIN:-trails.cool}
+      GRAFANA_USER: ${GRAFANA_USER:-admin}
+      GRAFANA_PASSWORD_HASH: ${GRAFANA_PASSWORD_HASH:-}
     volumes:
       - ./Caddyfile:/etc/caddy/Caddyfile:ro
       - caddy_data:/data

infrastructure/loki/loki-config.yml

@@ -30,3 +30,4 @@ limits_config:
 compactor:
   working_directory: /loki/compactor
   retention_enabled: true
+  delete_request_store: filesystem