feat: add Coolify deployment documentation (#39)

- Complete Coolify deployment guide (COOLIFY_DEPLOYMENT.md)
- Deployment checklist (DEPLOYMENT_CHECKLIST.md)
- Step-by-step Coolify setup
- Supabase configuration
- Environment variable setup
- Domain & SSL configuration
- Monitoring setup
- Troubleshooting guide
- Rollback procedures
- Security checklist
- Backup strategy
- Staging environment setup

Documentation covers:
- Git-based deployment
- Continuous deployment via webhooks
- Health checks and monitoring
- Performance optimization
- Cost estimates
- Post-deployment verification
- Common issues and solutions

Ready for production deployment to Coolify.

Closes #39

docs/DEPLOYMENT_CHECKLIST.md

@@ -0,0 +1,210 @@
+# Deployment Checklist
+
+Use this checklist to ensure a smooth deployment to production or staging.
+
+## Pre-Deployment
+
+### Code Quality
+- [ ] All tests passing (E2E_TESTING.md)
+- [ ] No critical bugs open
+- [ ] Code reviewed and approved
+- [ ] CHANGELOG.md updated
+- [ ] Version tagged in git
+
+### Database
+- [ ] Migrations tested locally
+- [ ] Migrations run on staging
+- [ ] Seed data prepared (if needed)
+- [ ] Backup created
+- [ ] RLS policies verified
+
+### Configuration
+- [ ] Environment variables documented
+- [ ] .env.production.example updated
+- [ ] Secrets not in repository
+- [ ] Docker files tested locally
+- [ ] Health check endpoint working
+
+### Documentation
+- [ ] DEPLOYMENT.md reviewed
+- [ ] README.md up to date
+- [ ] API changes documented
+- [ ] Known issues documented
+
+## Deployment
+
+### Coolify Setup
+- [ ] Resource created in Coolify
+- [ ] Git repository connected
+- [ ] Branch configured (main/develop)
+- [ ] docker-compose.prod.yml path set
+- [ ] Environment variables added
+- [ ] Domain configured (optional)
+- [ ] SSL enabled
+
+### Supabase Setup
+- [ ] Project created
+- [ ] Migrations run
+- [ ] RLS policies enabled
+- [ ] Auth providers configured
+- [ ] Storage buckets created
+- [ ] API keys copied
+
+### Build & Deploy
+- [ ] Triggered deployment
+- [ ] Build logs checked (no errors)
+- [ ] Container started successfully
+- [ ] Health check passes
+
+## Post-Deployment Verification
+
+### Health Checks
+- [ ] `/api/health` returns 200 OK
+- [ ] Homepage loads
+- [ ] Auth works (sign up/in)
+- [ ] Database connection works
+
+### PWA
+- [ ] Manifest loads correctly
+- [ ] Service worker registers
+- [ ] Install prompt appears
+- [ ] Offline mode works
+- [ ] Icons display correctly
+
+### Functionality
+- [ ] Can create account
+- [ ] Can sign in
+- [ ] Can add inventory item
+- [ ] Can edit item
+- [ ] Can delete item
+- [ ] Can add tags
+- [ ] Can scan barcode (if implemented)
+
+### Performance
+- [ ] Page load < 3s
+- [ ] Lighthouse score > 90 (PWA)
+- [ ] No console errors
+- [ ] No network errors
+
+### Cross-Browser
+- [ ] Chrome (desktop)
+- [ ] Firefox (desktop)
+- [ ] Safari (desktop)
+- [ ] Chrome (mobile)
+- [ ] Safari (iOS)
+
+## Monitoring
+
+### Setup
+- [ ] Uptime monitoring configured
+- [ ] Error tracking enabled (optional)
+- [ ] Log aggregation set up
+- [ ] Alerts configured
+- [ ] Metrics dashboard created (optional)
+
+### Checks
+- [ ] CPU usage normal
+- [ ] Memory usage normal
+- [ ] Disk space sufficient
+- [ ] No error spikes
+
+## Security
+
+### Verification
+- [ ] HTTPS enabled
+- [ ] SSL certificate valid
+- [ ] No credentials exposed
+- [ ] Firewall configured
+- [ ] Supabase RLS enabled
+- [ ] Strong admin passwords
+
+### Compliance
+- [ ] Privacy policy added (if required)
+- [ ] Terms of service added (if required)
+- [ ] Cookie notice (if applicable)
+- [ ] GDPR compliance (if EU users)
+
+## Communication
+
+### Team
+- [ ] Deployment announced
+- [ ] Access details shared
+- [ ] Rollback plan communicated
+- [ ] Support plan established
+
+### Users
+- [ ] Announcement prepared
+- [ ] Migration guide ready (if needed)
+- [ ] Support channels available
+- [ ] Feedback mechanism in place
+
+## Backup & Recovery
+
+### Backups
+- [ ] Database backup verified
+- [ ] Volume backup taken
+- [ ] Backup restore tested
+- [ ] Backup schedule configured
+
+### Disaster Recovery
+- [ ] Rollback plan documented
+- [ ] Emergency contacts listed
+- [ ] Recovery time objective (RTO) defined
+- [ ] Recovery point objective (RPO) defined
+
+## Post-Launch (24-48h)
+
+### Monitoring
+- [ ] Check logs for errors
+- [ ] Review uptime metrics
+- [ ] Analyze user behavior
+- [ ] Check resource usage
+
+### Optimization
+- [ ] Identify slow queries
+- [ ] Optimize heavy assets
+- [ ] Review caching strategy
+- [ ] Tune resource limits
+
+### Feedback
+- [ ] Collect user feedback
+- [ ] Log issues found
+- [ ] Prioritize fixes
+- [ ] Plan next iteration
+
+## Sign-Off
+
+**Deployed by:** ___________________  
+**Date:** ___________________  
+**Environment:** Production / Staging  
+**Version:** ___________________  
+**Status:** ✅ Success / ⚠️ Issues / ❌ Failed
+
+**Notes:**
+_____________________________________________
+_____________________________________________
+_____________________________________________
+
+**Next Review:** ___________________
+
+---
+
+## Rollback Criteria
+
+Trigger rollback if:
+- [ ] Critical bug discovered
+- [ ] Data loss occurring
+- [ ] Service unavailable > 15 min
+- [ ] Security vulnerability found
+- [ ] Performance degraded > 50%
+
+**Rollback Procedure:**
+1. In Coolify → Previous deployment → Redeploy
+2. Or: `git revert` and redeploy
+3. Notify team and users
+4. Investigate root cause
+5. Fix and redeploy
+
+---
+
+**Remember:** It's better to delay than to deploy broken code. Take your time with this checklist!