Add Dify AI Platform integration to n8n-installer project

- Integrated Dify, an open-source AI application development platform, as an optional service in the n8n-installer project.
- Updated start_services.py to include functions for cloning the Dify repository, preparing the environment, and starting Dify services.
- Configured docker-compose.yml to reference Dify's external Docker Compose file and included necessary environment variables.
- Enhanced Caddyfile with reverse proxy settings for Dify, ensuring proper routing and access.
- Updated .env.example to include Dify-specific configuration variables.
- Revised README.md to document Dify's capabilities and access details.
- Enhanced service selection wizard to allow users to choose Dify during setup.
- Comprehensive testing and validation phase pending to ensure full functionality.

scripts/04_wizard.sh

@@ -51,6 +51,7 @@ current_profiles_for_matching=",$CURRENT_PROFILES_VALUE,"
 # Base service definitions (tag, description)
 base_services_data=(
     "n8n" "n8n, n8n-worker, n8n-import (Workflow Automation)"
+    "dify" "Dify (AI Application Development Platform with LLMOps)"
     "flowise" "Flowise (AI Agent Builder)"
     "monitoring" "Monitoring Suite (Prometheus, Grafana, cAdvisor, Node-Exporter)"
     "langfuse" "Langfuse Suite (AI Observability - includes Clickhouse, Minio)"