Polish mobile responsive for bounty views

[sepulchralvoid666]

Closes #833

Wallet: 9PmjWFwM2mdnjBNjJyfNMTWGCnGAKFpywsLF9xcRF8PK

[nagiexplorer88]

This introduces an unconfigured Tailwind breakpoint. BountyCard.tsx now uses xs:inline and xs:hidden, but frontend/tailwind.config.js does not define an xs screen; it only extends theme values and relies on Tailwind defaults (sm, md, etc.).

That means the generated CSS will not include those xs: variants. In practice, hidden xs:inline stays hidden at every width, so the card loses the PRs label and the status text even on desktop. For #833 this should use an existing breakpoint such as sm: or add an xs screen to the Tailwind config.

[nagiexplorer88]

Confirmed. The follow-up commit replaces the unconfigured xs: classes in BountyCard.tsx with Tailwind default sm: variants:

<span className="hidden sm:inline">{bounty.submission_count} PRs</span>
<span className="sm:hidden">{bounty.submission_count}</span>
...
<span className="hidden sm:inline">{statusLabel}</span>

That addresses the missing generated CSS problem I pointed out; the hide/show classes now use a configured breakpoint.