Add deployment infrastructure and development guide

- db/migrations/: V001 (schema) + V002 (seed data) SQL files
- deploy/: systemd service files (taxbaik.service, taxbaik-admin.service)
- deploy/: Nginx location block configuration
- .gitea/workflows/deploy.yml: CI/CD pipeline (build, test, deploy)
- CLAUDE.md: Comprehensive development guidelines (9 sections)

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

deploy/taxbaik.service

@@ -0,0 +1,20 @@
+[Unit]
+Description=TaxBaik Public Website (.NET 8)
+After=network.target
+
+[Service]
+User=kjh2064
+WorkingDirectory=/home/kjh2064/taxbaik_active
+ExecStart=/usr/bin/dotnet TaxBaik.Web.dll
+Restart=always
+RestartSec=10
+KillSignal=SIGINT
+SyslogIdentifier=taxbaik
+Environment=ASPNETCORE_ENVIRONMENT=Production
+Environment=ASPNETCORE_URLS=http://127.0.0.1:5001
+# 아래 줄은 서버에서 직접 편집 (git에 커밋하지 않음)
+# Environment=ConnectionStrings__Default=Host=localhost;Database=taxbaikdb;Username=taxbaik;Password=CHANGE_ME
+Environment=DOTNET_PRINT_TELEMETRY_MESSAGE=false
+
+[Install]
+WantedBy=multi-user.target