fix(layout): prevent horizontal overflow in modals, sheets, and input fields

Modal overlay gets overflow: hidden; sheet scroll container gets overflow-x: hidden
to stop content bleed on narrow viewports. Inputs get min-width: 0 and
box-sizing: border-box so they cannot overflow two-column grid containers.

public/styles/layout.css

@@ -825,6 +825,7 @@
   display: flex;
   align-items: flex-end;
   justify-content: center;
+  overflow: hidden;
   animation: modal-overlay-in 0.2s ease forwards;
   /* iOS Safari: click-Events auf non-interactive divs erfordern cursor:pointer */
   cursor: pointer;
@@ -902,6 +903,7 @@
   flex: 1;
   min-height: 0;
   overflow-y: auto;
+  overflow-x: hidden;
   -webkit-overflow-scrolling: touch;
 }
 
@@ -1174,6 +1176,8 @@
 .input,
 .form-input {
   width: 100%;
+  min-width: 0;
+  box-sizing: border-box;
   padding: var(--space-2) var(--space-3);
   border-radius: var(--radius-sm);
   border: 1.5px solid var(--color-border);