📌 Description

This PR addresses issue #1253 by adding a Mermaid architecture diagram to the README.md to visually explain the CodeGraphContext workflow.

🚀 Changes Made

• Added an Architecture & Workflow section just before the "Supported Programming Languages" section.
• Implemented a beautifully styled Mermaid flowchart that clearly illustrates the data flow: from Source Code Parsing via Tree-sitter/SCIP, to Knowledge Graph generation, Database storage, and finally querying through the CLI Toolkit and MCP Server for AI Assistants.
• Applied custom CSS classes (classDef) within the Mermaid diagram to give it a modern dark-mode aesthetic (purple/blue accents) that matches the project's branding.

✅ Expected Outcome

• New users can now quickly understand how the different components of CodeGraphContext interact at a glance.
• Reduces the cognitive load required to understand the system architecture compared to reading multiple text sections.

Resolves #1253