Implement fullstack education catalog with disease detail pages, API routes, and shared types

- Add disease detail page component with data fetching and error handling
- Create shared types for diseases and classifications
- Implement API routes for diseases, classifications, and dashboard summary
- Develop reusable components for risk badge and disease card
- Build catalog page with search and filter functionality
- Update dashboard page with data-backed summary and manual classification form
- Register new routes in the web application
- Ensure type safety and consistency across shared modules

apps/api/src/lib/http-errors.ts

@@ -0,0 +1,20 @@
+export function badRequest(message: string): Response {
+  return new Response(JSON.stringify({ error: message }), {
+    status: 400,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}
+
+export function notFound(message: string): Response {
+  return new Response(JSON.stringify({ error: message }), {
+    status: 404,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}
+
+export function serviceUnavailable(message: string): Response {
+  return new Response(JSON.stringify({ error: message }), {
+    status: 503,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}