alt prop warning in build

Let's fix this:

```
WARNING in src/App.tsx
Line 61:19: img elements must have an alt prop, either with meaningful text, or an empty string for decorative images jsx-a11y/alt-text
```

This is the logo-- I think we can count that as "decorative" and use an empty string.

Open src/App.tsx at line 61 and inspect the logo image mentioned in the warning. Add the appropriate empty alt value for this decorative image, then run the build and confirm the jsx-a11y/alt-text warning is gone.

Written by the indexing model from the issue text.