refactor: remove unused mermaid diagrams and scripts (#535)

# Remove Mermaid Diagram Compilation Scripts and Files

This PR removes unused Mermaid diagram compilation scripts and generated SVG files from the website package. The changes include:

1. Deleting the `mmdc-compile` and `mmdc-watch` scripts from the `bin` directory
2. Removing the `gen-diagram` script from `package.json`
3. Deleting all generated SVG diagram files from the `public/diagrams` directory
4. Removing all Mermaid source files from `src/assets`
5. Replacing Mermaid diagram references in documentation with D2 diagrams

The D2 diagram syntax has been preserved in the documentation files, ensuring that the visual content remains available but is now using the preferred diagramming tool.

Author: jumski

pkgs/website/bin/mmdc-compile

@@ -9,8 +9,7 @@
     "start": "astro dev",
     "build": "astro check && astro build",
     "preview": "astro preview",
-    "astro": "astro",
-    "gen-diagram": "mmdc --backgroundColor='#121a19' --theme neutral --output public/analyze_website.svg < m.mermaid"
+    "astro": "astro"
   },
   "dependencies": {
     "@astrojs/check": "^0.9.4",