feat(ui): add dashboard sections with sidebar navigation and mock views

Add seven sidebar sections (Dashboard, Providers, Chat, Tools,
Knowledge Base, Developer, Organization) with fully rendered mock views,
nested sub-shells for Developer and Organization, and SearXNG container
for future news feed integration. Replaces the previous OverviewPage
with a news feed dashboard.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -28,4 +28,15 @@ services:
       - 27017:27017
     environment:
       MONGO_INITDB_ROOT_USERNAME: root
-      MONGO_INITDB_ROOT_PASSWORD: example
+      MONGO_INITDB_ROOT_PASSWORD: example
+
+  searxng:
+    image: searxng/searxng:latest
+    container_name: certifai-searxng
+    restart: unless-stopped
+    ports:
+      - "8888:8080"
+    environment:
+      - SEARXNG_BASE_URL=http://localhost:8888
+    volumes:
+      - ./searxng:/etc/searxng:rw