feat(6): phase 6 plan 02 - operational runbook and documentation

- Created OPERATIONAL_RUNBOOK.md: comprehensive step-by-step procedures for both Docker and Standalone deployment modes covering deployment, daily ops, troubleshooting, backup/restore, disaster recovery, scaling, and updates
- Created HEALTH_MONITORING_CHECKLIST.md: daily/weekly/monthly health check procedures with alert thresholds and quick troubleshooting reference
- Created DISASTER_RECOVERY_PLAN.md: detailed procedures for 6 failure scenarios (database corruption, hardware failure, data center failure, app crash, disk full, network isolation) with RTO/RPO targets
- Created CONFIGURATION_REFERENCE.md: complete documentation of all inventory.env parameters for both deployment modes with common scenarios and troubleshooting
- Created EMERGENCY_PROCEDURES.md: quick-reference incident response playbook with 7 critical scenarios, decision tree, escalation path, and printable cheat sheet
- Created scripts/backup.sh: automated backup script supporting both Docker and Standalone with integrity verification and retention management
- Created scripts/restore.sh: restore script with triple confirmation, safety backups, and validation tests for both deployment modes
- Created config/backup-cron.sh: installer for daily/weekly automated backup cron jobs (2 AM daily, 3 AM Sunday)

All documentation covers dual-deployment modes with shared configuration files.
Documentation is operator-ready with copy-paste commands and clear expected outputs.

frontend/Dockerfile

@@ -1,5 +1,10 @@
 FROM node:20-alpine AS base
 
+# Metadata labels
+LABEL maintainer="TFM aInventory Team"
+LABEL version="2.0.0"
+LABEL description="TFM aInventory Frontend Web Service"
+
 # Step 1: Install dependencies
 FROM base AS deps
 RUN apk add --no-cache libc6-compat
@@ -19,7 +24,7 @@ RUN npm run build
 
 # Step 3: Production image
 FROM base AS runner
-RUN apk add --no-cache su-exec
+RUN apk add --no-cache su-exec curl
 WORKDIR /app
 
 ENV NODE_ENV production
@@ -47,5 +52,8 @@ EXPOSE 3000
 ENV PORT 3000
 ENV HOSTNAME "0.0.0.0"
 
-ENTRYPOINT ["/app/entrypoint.sh"]
+# Health check — verify frontend is responsive
+HEALTHCHECK --interval=30s --timeout=10s --start-period=40s --retries=3 \
+    CMD curl -f http://localhost:3000/ || exit 1
 
+ENTRYPOINT ["/app/entrypoint.sh"]