js-dos v8 uses DaisyUI which sets text-transform:uppercase, height:3rem
on .btn — these cascade through even after our specificity fix because
we didn't define those properties. Added explicit overrides.
The Play page injects js-dos CSS from CDN which has its own .btn
rules. Because it loads after the app CSS, it was overriding the
custom phosphor-green button styles (including the Upload button
in the header).
Fixed by doubling the class selector (.btn.btn) to raise specificity
to (0,2,0), which beats injected CSS regardless of load order.
droideparanoico