Revise or remove MuiDemo components for MUI v7



### 7. **Update `MuiDemo/` or remove legacy demo code**

**Why:**
This folder explicitly references MUI and is likely outdated.

**Scope:**

* Either upgrade demo components to MUI v7
* Or remove if no longer relevant
* Use it as a sandbox to validate MUI v7 patterns

**Suggested title:**
**Revise or remove MuiDemo components for MUI v7**

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