refactor: streaming download, Git LFS templates, deploy workflow

- Replace base64 JSON response with StreamingResponseBody (zero-buffer)
- Error responses return JSON via GlobalExceptionHandler (400/404)
- Add git-lfs track for *.docx to keep repo lean
- Add deploy/deploy.sh: one-click build + restart
- Add deploy/clean-lfs.sh: periodic LFS cache cleanup
- Add deploy/gmp-service.service: systemd service unit
- Remove unused ApiResponse and DocxExportData DTOs
- Fix build.sh/run.sh jar name (gmp-mock-service -> gmp-service)
- Add TemplateNotFoundException for missing templates

deploy/gmp-service.service

@@ -0,0 +1,19 @@
+[Unit]
+Description=GMP Mock Service - Spring Boot Application
+Documentation=
+After=network.target
+
+[Service]
+Type=simple
+User=agentuser
+WorkingDirectory=/opt/gmp-service
+ExecStart=/usr/bin/java -Xms256m -Xmx512m -jar /opt/gmp-service/gmp-service.jar
+ExecStop=/bin/kill -SIGTERM $MAINPID
+SuccessExitStatus=143
+Restart=on-failure
+RestartSec=10
+StandardOutput=append:/var/log/gmp-service/stdout.log
+StandardError=append:/var/log/gmp-service/stderr.log
+
+[Install]
+WantedBy=multi-user.target