fix: add horizontal scroll to SimpleTable for mobile

[gaghan430]

Summary

Change overflow-hidden to overflow-x-auto on the SimpleTable wrapper so tables with 3+ columns scroll horizontally on mobile instead of clipping.

Only one usage exists: the nameservers table in project/detail/dns/detail.tsx (4 columns: Type, Value, DNS Host, Registrar). The sticky actions column pattern already works with this change.

Closes #407

Test plan

• Visit a DNS zone detail page with nameservers → table scrolls horizontally on mobile
• Desktop: unchanged

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