fix: prevent masonry layout shift on infinite scroll

Added overflow-y: scroll to html element to always reserve scrollbar
space. When content grows beyond viewport, the scrollbar appearance
would reduce container width by ~17px, causing CSS column masonry to
recalculate and shift items leftward. Fixes #146.

MilkStream.Client/Styles/_custom.scss

@@ -329,12 +329,13 @@ $btn-theme-colors: (
 }
 
 // ── Inter font overrides ──
-html, body {
+html {
+  overflow-y: scroll;
   font-family: 'Inter', 'Helvetica Neue', Helvetica, Arial, sans-serif;
-  min-height: 100dvh;
 }
-
 body {
+  font-family: inherit;
+  min-height: 100dvh;
   display: flex;
   flex-direction: column;
   background: radial-gradient(ellipse at 50% 0%,