feat: add privacy-safe server diagnostics

.env.example

@@ -1,4 +1,5 @@
 NODE_ENV=production
+DEPLOYMENT_REVISION=local-development
 HOST=0.0.0.0
 PORT=8786
 APP_ORIGIN=https://business.example.internal
@@ -54,3 +55,6 @@ ERP_RECONCILIATION_MAINTENANCE_TIMEOUT_MS=1800000
 DATA_RETENTION_ENABLED=false
 DATA_RETENTION_DAYS=180
 LOG_LEVEL=info
+# Docker json-file retention; these are consumed by Compose, not the app.
+LOG_MAX_SIZE=20m
+LOG_MAX_FILES=10