Fix header overlapping content at mobile breakpoints

In the SM (≤767px) and XS (≤479px) media queries, .lt-container { padding }
shorthand appeared after .lt-main { padding-top } with equal specificity,
causing the shorthand to clobber the header-clearance padding-top. Swap order
so .lt-main always wins.

Also remove redundant lt-scanlines div — body::before in base.css already
renders the scanline overlay globally.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

assets/css/base.css

@@ -2042,9 +2042,9 @@ select option:checked {
 /* ── SM — phones 480–767px ── */
 @media (max-width: 767px) {
   :root { --header-height: 50px; }
-  .lt-main { padding-top: calc(50px + var(--space-md)); }
-
   .lt-container { padding: var(--space-md); }
+  /* lt-main must come after lt-container so padding-top isn't clobbered by the shorthand */
+  .lt-main { padding-top: calc(50px + var(--space-md)); }
   .lt-header { padding: 0 var(--space-md); }
   .lt-brand-subtitle { display: none; }
 
@@ -2142,9 +2142,9 @@ select option:checked {
 /* ── XS — tiny phones ≤ 479px ── */
 @media (max-width: 479px) {
   :root { --header-height: 46px; }
-  .lt-main { padding-top: calc(46px + var(--space-sm)); }
-
   .lt-container { padding: var(--space-sm); }
+  /* lt-main must come after lt-container so padding-top isn't clobbered by the shorthand */
+  .lt-main { padding-top: calc(46px + var(--space-sm)); }
   .lt-stats-grid { grid-template-columns: 1fr 1fr; gap: var(--space-xs); }
   .lt-stat-card { padding: var(--space-xs) var(--space-sm); }
   .lt-stat-value { font-size: 1.4rem; }