Give the tech radar its own page

/radar (/en/radar, /ca/radar) shows every technology the collective has
placed, by ring: logo, category, what it is, why it sits there, its
website and how many projects use it. The landing's radar summary links
to it.

It is the first listing — a page this site composes rather than one
record's — so resolveRoute learns about those (LISTINGS), and builds
their addresses and hreflang alternates from the same table.

Logos sit on a light tile in both themes. A brand's mark is not ours to
recolour, and Rust's, which is black, would vanish in dark mode.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

landing/src/app/core/routes.spec.ts

@@ -1,7 +1,13 @@
 import { describe, expect, it } from 'vitest';
 
 import { DEFAULT_LOCALE, SUPPORTED_LOCALES } from './api';
-import { homeHref, resolveRoute, SECTIONS } from './routes';
+import {
+  homeHref,
+  listingAlternates,
+  listingPath,
+  resolveRoute,
+  SECTIONS,
+} from './routes';
 
 describe('resolveRoute', () => {
   it('reads a page at the root as the default language', () => {
@@ -77,6 +83,33 @@ describe('resolveRoute', () => {
   });
 });
 
+describe('listings', () => {
+  it('reads the radar in every language, before any page of that slug', () => {
+    expect(resolveRoute('/radar')).toEqual({
+      type: 'radar',
+      locale: 'es',
+      slug: '',
+    });
+    expect(resolveRoute('/ca/radar')).toEqual({
+      type: 'radar',
+      locale: 'ca',
+      slug: '',
+    });
+  });
+
+  it('builds the address resolveRoute reads back', () => {
+    for (const locale of SUPPORTED_LOCALES) {
+      expect(resolveRoute(listingPath('radar', locale))?.type).toBe('radar');
+    }
+
+    expect(listingAlternates('radar')).toEqual({
+      es: '/radar',
+      en: '/en/radar',
+      ca: '/ca/radar',
+    });
+  });
+});
+
 describe('homeHref', () => {
   it('answers on ?lang= for every language but the default', () => {
     expect(homeHref(DEFAULT_LOCALE)).toBe('/');