Add filter options to the entities APIs (MCP servers, virtual servers, tools, prompts, resources, a2a...).

🧭 Type of Feature

Please select the most appropriate category:

• Enhancement to existing functionality
• New feature or capability
• New MCP-compliant server
• New component or integration
• Developer tooling or test improvement
• Packaging, automation and deployment (ex: pypi, docker, quay.io, kubernetes, terraform)
• Other (please describe below)

📓 Additional Context

We need to define what attributes are filterable. All? Core ones (id/title/description)? Anything else?