Fix admin table columns hidden on overflow instead of scrollable

[calebyhan]

Summary

• DataTable.tsx clipped table overflow with overflow-hidden instead of allowing horizontal scroll, and cells use whitespace-nowrap, so long field values pushed trailing columns (type/status/actions) off-screen with no way to reach them.
• Switched the container to overflow-x-auto (dropping overflow-hidden) and added min-w-max to the table so it doesn't compress below content width.
• This is a shared component used by all 9 admin tables (events, senators, legislation, news, districts, accounts, leadership, static-pages, staff), so the fix applies everywhere at once.

Fixes #199

Test plan

• tsc --noEmit passes
• Frontend build passes
• Manually verify the events table (and a couple others) scroll horizontally on a narrow viewport instead of hiding the actions column

[github-actions]

Test Results

573 tests  ±0   573 ✅ ±0   49s ⏱️ ±0s
  1 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit f3c1047. ± Comparison against base commit 9526ecc.

[MasonMines2006]

LGTM