[ui] Highlight Trade button with green accent in mobile action bar

[realproject7]

Summary

On the mobile floating bottom bar, the Trade button should stand out from Donate and Rate by using the green accent color for both text and border.

Current

All three buttons (Trade, Donate, Rate) have the same muted border/text styling.

Desired

• Trade button: green accent border (border-accent) + green accent text (text-accent)
• Donate and Rate: keep current muted styling

File: src/components/MobileActionBar.tsx

Acceptance Criteria

• Trade button has green accent border and text
• Donate and Rate buttons unchanged
• Looks correct on all mobile widths

Labels

agent/T3, plotlink, ui