docs: Update Mermaid diagrams with design token styling

[beginwebdev2002]

Applies standard design token class definitions (default, component, layout) using soft pastel colors and clear dark text across valid Mermaid diagrams (graphs and flowcharts) in all Markdown files. The design tokens are assigned to nodes automatically, avoiding unsupported diagrams like sequenceDiagram to ensure parsing integrity. This addresses the request to update mermaid diagrams across the project based on the UI/UX design rules.

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PR created automatically by Jules for task 14301499361998250830 started by @beginwebdev2002

[google-labs-jules]

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