Enrich the landing page with a bento grid and aurora atmosphere

Close the flat-vs-adaline gap by adding depth and motion to our product shots:
- bento: replace the flat stacked features with a varied 12-column grid (org
  chart, cost, office, messages, connectors, plus a local-first highlight card),
  each with a corner glow and hover
- showcase: a dark aurora "Set the goal" statement band (Newsreader serif over a
  drifting northern-lights glow) for a light -> dark -> light rhythm
- hero + footer: aurora glow staging behind the dashboard and under the CTA
- ui/aurora + globals: mint/teal/lime drift-animated glow tokens
- remove the superseded flat feature components

e2e green (12 passed); build verified.

landing/components/ui/aurora.tsx

@@ -0,0 +1,20 @@
+/**
+ * Northern-lights glow for dark showcase surfaces: three soft, slowly drifting
+ * radial blooms in mint / teal / lime. Purely decorative.
+ */
+export function Aurora({ className = "" }: { className?: string }) {
+  return (
+    <div aria-hidden="true" className={`pointer-events-none absolute inset-0 overflow-hidden ${className}`}>
+      <div
+        className="aurora-layer absolute -inset-[25%]"
+        style={{
+          filter: "blur(56px)",
+          background:
+            "radial-gradient(42% 55% at 22% 62%, var(--aurora-mint) 0%, transparent 62%)," +
+            "radial-gradient(38% 50% at 72% 38%, var(--aurora-teal) 0%, transparent 60%)," +
+            "radial-gradient(34% 44% at 52% 84%, var(--aurora-lime) 0%, transparent 58%)",
+        }}
+      />
+    </div>
+  );
+}