Rebuild navbar, hero, and feature sections in adaline style

- navbar: sticky, transparent to blur-on-scroll, wordmark + mono nav links +
  theme toggle + Download CTA, Reicon Menu/Xmark icons (components/layout)
- theme-toggle: Reicon Sun/Moon icons
- hero: meadow badge, tight Instrument Sans headline, Download + How-it-works
  CTAs, availability line, framed dashboard shot (components/sections)
- features: five stacked heading-over-panel sections mapping the org chart,
  office, messages, connectors and cost-control screens
- ui/media-frame: shared framed product-shot panel
- reveal: progressive enhancement — content is visible without JS and only
  hidden once the js class is present, then revealed on scroll
- remove the superseded flat navbar/hero/features components

Verified: next build green; desktop + mobile screenshots reviewed.

landing/components/sections/feature-section.tsx

@@ -0,0 +1,18 @@
+import { Reveal } from "../ui/reveal";
+import { SectionHeading } from "../ui/section-heading";
+import { MediaFrame } from "../ui/media-frame";
+import type { FeatureSection as FeatureSectionData } from "../../lib/landing-content";
+
+/** One feature: heading + subhead above a full-width product panel (adaline rhythm). */
+export function FeatureSection({ feature }: { feature: FeatureSectionData }) {
+  return (
+    <div id={feature.id} className="flex scroll-mt-24 flex-col gap-8 md:gap-10">
+      <Reveal>
+        <SectionHeading eyebrow={feature.eyebrow} title={feature.title} description={feature.description} />
+      </Reveal>
+      <Reveal delay={90}>
+        <MediaFrame src={feature.image} alt={feature.imageAlt} />
+      </Reveal>
+    </div>
+  );
+}