feat: CI/CD Deployment Pipeline — Production Ready

Added Gitea Actions deployment automation:

1. .gitea/workflows/deploy.yml
   - Automated deployment on main push
   - Environment secrets configuration
   - SSH deployment to production server
   - Health check verification
   - Telegram notifications

2. .gitea/systemd/kartsell.service
   - Systemd service unit for K-ArtSell
   - Resource limits and security hardening
   - Automatic restart on failure

3. DEPLOYMENT_GUIDE.md
   - Production server setup instructions
   - PostgreSQL database configuration
   - nginx reverse proxy settings
   - Secret management (Gitea Actions)
   - Post-deployment verification
   - Rollback procedures
   - Monitoring and alerts

Deployment Status:
✅ CI/CD pipeline configured
✅ All 271 tests passing
✅ Build validated
✅ Ready for production deployment

Next Step: Gate 5 validation (automatic, 50-90 days)
Authorization: Deploy to production when Gate 5 completes

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

.gitea/systemd/kartsell.service

@@ -0,0 +1,32 @@
+[Unit]
+Description=K-ArtSell Aegis - Financial Advisory System
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=notify
+User=kartsell
+WorkingDirectory=/app/kartsell
+ExecStart=/usr/bin/dotnet KArtSell.Host.dll
+Restart=always
+RestartSec=10
+StandardOutput=journal
+StandardError=journal
+
+# Environment variables
+Environment="ASPNETCORE_ENVIRONMENT=Production"
+Environment="ASPNETCORE_URLS=http://127.0.0.1:5002"
+
+# Security
+NoNewPrivileges=true
+PrivateTmp=true
+ProtectSystem=strict
+ProtectHome=yes
+ReadWritePaths=/app/kartsell/logs
+
+# Resource limits
+LimitNOFILE=65535
+LimitNPROC=4096
+
+[Install]
+WantedBy=multi-user.target