feat(analytics): retire Rybbit and add SEO/GEO discovery tracking

Document Umami as the sole analytics platform, remove Rybbit proxy and
tracker code, and classify public page traffic with discovery_channel for
adm SEO/GEO dashboards.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/portal-domain-services-bootstrap.test.mjs

@@ -61,8 +61,6 @@ function createBootstrapSetup(overrides = {}) {
     env: {
       H5_DEFAULT_TIMEZONE: 'Asia/Singapore',
       PLAZA_REDIS_URL: 'redis://plaza',
-      MEMIND_RYBBIT_ENABLED: 'true',
-      MEMIND_RYBBIT_SITE_ID: '2',
     },
     runtime: {
       maxFileBytes: 100,
@@ -325,9 +323,6 @@ test('domain bootstrap preserves schema and service assembly order', async () =>
     result.mindSpaceAnalyticsConfig.scriptPath,
     '/analytics/script.js',
   );
-  assert.equal(result.mindSpaceRybbitConfig.enabled, true);
-  assert.equal(result.mindSpaceRybbitConfig.siteId, '2');
-  assert.equal(result.mindSpaceRybbitConfig.idSecret, 'secret-1');
 });
 
 test('domain bootstrap preserves delayed user, snapshot, and Page Data dependencies', async () => {