fix(dashboard): scope h-full to xl + tighter mobile sizing on KPIs

The Alerts rail and Reminders rail were using h-full unconditionally, which
worked at xl: where the dashboard grid pairs them with a sibling chart
column, but produced weirdly stretched empty cards in the single-column
mobile stack (no fixed-height context to fill).

  alert-rail / my-reminders-rail: h-full -> xl:h-full

KPI tiles + skeleton rendered the same desktop padding (p-5) and font sizes
on phone, leaving the value cramped against a wide white frame. Tighter
mobile defaults that scale up at sm:

  KPITile      p-3 sm:p-5, label text-[10px] sm:text-xs,
               value mt-1 text-lg sm:mt-2 sm:text-2xl, value truncates
  KpiTileSkeleton: matching p-3 sm:p-5 + smaller skeleton bars on mobile

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/dashboard/kpi-cards.tsx

@@ -28,11 +28,10 @@ function formatPercent(value: number): string {
 
 function KpiTileSkeleton() {
   return (
-    <div className="relative overflow-hidden rounded-xl border border-border bg-card p-5 shadow-sm">
+    <div className="relative overflow-hidden rounded-xl border border-border bg-card p-3 shadow-sm sm:p-5">
       <div className="absolute inset-x-0 top-0 h-1 bg-muted" aria-hidden />
-      <Skeleton className="h-3 w-24" />
-      <Skeleton className="mt-3 h-7 w-32" />
-      <Skeleton className="mt-2 h-3 w-12" />
+      <Skeleton className="h-3 w-20" />
+      <Skeleton className="mt-2 h-6 w-24 sm:mt-3 sm:h-7" />
     </div>
   );
 }

src/components/dashboard/my-reminders-rail.tsx

@@ -67,8 +67,11 @@ export function MyRemindersRail() {
     return `/${portSlug}/reminders`;
   }
 
+  // `h-full` only at xl: where the dashboard grid pairs this rail with
+  // a sibling chart column. On mobile (stacked) it produced a weirdly
+  // tall empty card.
   return (
-    <Card className="h-full">
+    <Card className="xl:h-full">
       <CardHeader className="flex flex-row items-start justify-between gap-2 space-y-0 pb-3">
         <div className="space-y-0.5">
           <CardTitle className="flex items-center gap-1.5 text-base">