feat(nessa): add branded landing page with site-aware metadata

Add the Nessa subdomain landing page served at nessa.freno.me/.

- index.tsx: hero, feature highlights, CTA band, and footer themed via
  useSite() brandColor and useDarkMode(); deliberately avoids freno.me
  web-auth UI (Nessa uses Clerk) and uses a non-fabricated 'Coming soon'
  CTA since there's no app-store presence yet.
- meta.ts: deterministic PageHeadProps (title, description, OG) as a pure
  module mirroring the page-head-meta testability pattern; feature copy is
  derived from real nessaCommunityRouter capabilities (clubs, challenges,
  social.feed, events).
- meta.test.ts: resolves metadata over SITE_CONFIG.nessa + pathname '/' to
  assert title suffix composition, canonical, OG image fallback, and
  description content.

src/routes/nessa/meta.test.ts

@@ -0,0 +1,51 @@
+/**
+ * Unit tests for the Nessa landing page metadata (task 07).
+ *
+ * Asserts the task-spec unit criterion: "PageHead on nessa site produces
+ * correct title suffix and canonical." Mirrors the `page-head-meta.ts`
+ * testability pattern — `nessa/meta.ts` is a pure module (no solid-js /
+ * @solidjs/router / @solidjs/meta imports) so `bun:test` can resolve it.
+ *
+ * The resolved values are produced by the (task-02) `resolvePageHeadMeta`
+ * helper over `NESSA_LANDING_META` + `SITE_CONFIG.nessa` + the browser
+ * pathname `/` — exactly what `<PageHead>` emits on `nessa.freno.me/`.
+ */
+import { describe, it, expect } from "bun:test";
+import { resolvePageHeadMeta } from "~/components/page-head-meta";
+import { SITE_CONFIG } from "~/lib/site-context";
+import { NESSA_LANDING_META } from "./meta";
+
+describe("Nessa landing page — PageHead metadata", () => {
+  it("title composes to 'Nessa | Nessa' (base title + nessa titleSuffix)", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.title).toBe("Nessa | Nessa");
+  });
+
+  it("title contains the substring 'Nessa'", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.title).toContain("Nessa");
+  });
+
+  it("canonical is https://nessa.freno.me/ for the landing route", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.canonical).toBe("https://nessa.freno.me/");
+  });
+
+  it("ogImage falls back to the nessa site default", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.ogImage).toBe(SITE_CONFIG.nessa.ogDefaultImage);
+  });
+
+  it("ogTitle uses the explicit marketing copy, not the bare title", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.ogTitle).toBe(NESSA_LANDING_META.ogTitle);
+    expect(meta.ogTitle).not.toBe("Nessa");
+  });
+
+  it("description mentions community capabilities", () => {
+    const meta = resolvePageHeadMeta(NESSA_LANDING_META, SITE_CONFIG.nessa, "/");
+    expect(meta.description).toBe(NESSA_LANDING_META.description);
+    expect(meta.description?.toLowerCase()).toContain("community");
+    expect(meta.description?.toLowerCase()).toContain("challenges");
+  });
+});