Revamp README.md with expanded release notes and agentic examples

- Update README structure for clarity and relevance.
- Add in-depth examples of Sampling Client and agentic tools (e.g., `CodeAnalyzerTool`, `SupportAgent`).
- Highlight advanced features like sampling-driven decision-making and dynamic resource management.
- Include quick-start guide, architecture overview, and resource links.
- Position Symfony MCP Server as a foundation for building intelligent AI agents.

Author: klapaudius