Match panel heights in Add-server / How-ranking-works grid

align-items:start made each .panel size to its own content, so the
two side-by-side cards in .add-grid ended up with different heights
whenever their text length differed. Switch to align-items:stretch
(+ flex column on the panels) so both cards always match height.

index.html

@@ -117,7 +117,8 @@ tbody tr:hover{background:color-mix(in srgb,var(--accent-soft) 50%,transparent)}
 .num{font-family:var(--mono);font-variant-numeric:tabular-nums}
 .score{font-family:var(--display);font-weight:600;font-size:15px}
 
-.add-grid{display:grid;grid-template-columns:1.3fr 1fr;gap:24px;margin:40px 0;align-items:start}
+.add-grid{display:grid;grid-template-columns:1.3fr 1fr;gap:24px;margin:40px 0;align-items:stretch}
+.add-grid>.panel{display:flex;flex-direction:column}
 .panel{
   background:var(--panel);border:1px solid var(--line);
   border-radius:var(--radius);padding:24px;box-shadow:var(--shadow);