LCORE-275: Add A2A Support

[luis5tb]

Description

This PR is adding A2A wrapper to streaming_query_v2 so that agents created can be consumed using the standard A2A endpoints. It is adding 2 endpoints:

• Unauthenticated one to return the Agent Card
• Authenticated one to reach out the A2A endpoint

Type of change

• Refactor
• New feature
• Bug fix
• CVE fix
• Optimization
• Documentation Update
• Configuration Update
• Bump-up service version
• Bump-up dependent library
• Bump-up library or tool used for development (does not change the final image)
• CI configuration change
• Konflux configuration change
• Unit tests improvement
• Integration tests improvement
• End to end tests improvement

Related Tickets & Documents

• Related Issue #
• Closes #

Checklist before requesting a review

• I have performed a self-review of my code.
• PR has passed all pre-merge test jobs.
• If it is a core feature, I have added thorough tests.

Testing

• Please provide detailed steps to perform tests related to this code change.
• How were the fix/results from this change verified? Please provide relevant screenshots or results.

Summary by CodeRabbit

• New Features

  • Full Agent-to-Agent (A2A) support: agent discovery, JSON‑RPC messaging, streaming and buffered task execution, multi‑turn conversations, agent card and health endpoints.

• Configuration

  • service.base_url option; A2A state configuration with memory, SQLite and PostgreSQL backends; example YAMLs and agent‑card options.

• Dependencies

  • Added async DB drivers and YAML support.

• Documentation

  • Comprehensive A2A protocol guide and endpoint docs.

• Tests

  • New unit tests covering A2A flows and storage backends.

_{✏️ Tip: You can customize this high-level summary in your review settings.}