refactor(demo): replace Portainer with Dockhand

Replace Portainer container management service with Dockhand:
- Update docker-compose.yml.template with Dockhand service definition
- Replace portainer_data volume with dockhand_data
- Update PORTAINER_PORT to DOCKHAND_PORT in demo.env
- Update all script references (demo-stack.sh, demo-test.sh, validate-all.sh)
- Update integration test from Portainer to Dockhand
- Update documentation files (README.md, AGENTS.md, api-docs,
  service-guides, troubleshooting)

Dockhand provides modern Docker management UI with:
- Container lifecycle management
- Compose stack orchestration
- Git-based deployments
- Multi-environment support
- Terminal access and log streaming
- File browser capabilities

Maintains same port (4007) for consistency.

💘 Generated with Crush

Assisted-by: GLM-4.7 via Crush <crush@charm.land>

demo/docker-compose.yml.template

@@ -17,8 +17,9 @@ volumes:
     driver: local
   ${COMPOSE_PROJECT_NAME}_pihole_data:
     driver: local
-  ${COMPOSE_PROJECT_NAME}_portainer_data:
+  ${COMPOSE_PROJECT_NAME}_dockhand_data:
     driver: local
+
   ${COMPOSE_PROJECT_NAME}_influxdb_data:
     driver: local
   ${COMPOSE_PROJECT_NAME}_grafana_data:
@@ -128,29 +129,30 @@ services:
       timeout: ${HEALTH_CHECK_TIMEOUT}
       retries: ${HEALTH_CHECK_RETRIES}
 
-  # Portainer - Container Management
-  portainer:
-    image: portainer/portainer-ce:latest
-    container_name: "${COMPOSE_PROJECT_NAME}-portainer"
+  # Dockhand - Docker Management
+  dockhand:
+    image: fnsys/dockhand:latest
+    container_name: "${COMPOSE_PROJECT_NAME}-dockhand"
     restart: unless-stopped
     networks:
       - ${COMPOSE_NETWORK_NAME}
     ports:
-      - "${PORTAINER_PORT}:9000"
+      - "${DOCKHAND_PORT}:3000"
     volumes:
-      - ${COMPOSE_PROJECT_NAME}_portainer_data:/data
+      - ${COMPOSE_PROJECT_NAME}_dockhand_data:/app/data
+      - /var/run/docker.sock:/var/run/docker.sock
     environment:
       - PUID=${DEMO_UID}
       - PGID=${DEMO_GID}
     labels:
       homepage.group: "Infrastructure"
-      homepage.name: "Portainer"
-      homepage.icon: "portainer"
-      homepage.href: "http://localhost:${PORTAINER_PORT}"
-      homepage.description: "Web-based container management"
+      homepage.name: "Dockhand"
+      homepage.icon: "dockhand"
+      homepage.href: "http://localhost:${DOCKHAND_PORT}"
+      homepage.description: "Modern Docker management UI"
     healthcheck:
       test: ["CMD", "wget", "--no-verbose", "--tries=1", "--spider",
-             "http://localhost:9000"]
+             "http://localhost:3000"]
       interval: ${HEALTH_CHECK_INTERVAL}
       timeout: ${HEALTH_CHECK_TIMEOUT}
       retries: ${HEALTH_CHECK_RETRIES}