feat: persist authenticated diagnoses

Implement diagnosis persistence routes with image upload, classification,
and prediction storage. Add missing HTTP error helpers (unauthorized,
forbidden) and update uploader client to use configurable base URL.

- Create POST /api/v1/diagnoses to upload images and store classifications
- Create GET /api/v1/diagnoses to list user's diagnoses (30 most recent)
- Create GET /api/v1/diagnoses/:id to retrieve diagnosis with predictions
- Add loadDiagnosisRecord helper for consistent diagnosis data loading
- Update uploader-client.ts to use env.uploaderBaseUrl
- Add unauthorized and forbidden error helpers to http-errors.ts
- Register diagnosisRoutes in main app

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -5,6 +5,20 @@ export function badRequest(message: string): Response {
   });
 }
 
+export function unauthorized(message: string): Response {
+  return new Response(JSON.stringify({ error: message }), {
+    status: 401,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}
+
+export function forbidden(message: string): Response {
+  return new Response(JSON.stringify({ error: message }), {
+    status: 403,
+    headers: { 'Content-Type': 'application/json' },
+  });
+}
+
 export function notFound(message: string): Response {
   return new Response(JSON.stringify({ error: message }), {
     status: 404,