fix(ssr): center the client bank-account sub-editor content

The bank-account editor (cash/credit/checking) is a full sub-modal that swaps
into the client wizard at the same 820px width, but its single-column form
(~430px of fields) hugged the far-left edge, leaving the whole right half empty —
the same "too wide / empty" look as the pay modal. Constrain the form to max-w-xl
and center it (mx-auto) so the whitespace is balanced; keeps the 820px card so
there's no size jump entering/leaving the editor.

Audit context: walked all 7 client steps + the pay wizard (step 1 + step 2
simple/advanced grid) at 1440x900 — all fit with no overflow; the regular steps
stay balanced via the vertical timeline sidebar. This sub-editor was the one
unbalanced spot.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

resources/public/output.css

@@ -1694,6 +1694,10 @@ input:checked + .toggle-bg {
   max-width: 1024px;
 }
 
+.max-w-xl {
+  max-width: 36rem;
+}
+
 .max-w-xs {
   max-width: 20rem;
 }