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/index.ts

@@ -4,6 +4,7 @@ import { healthRoutes } from './routes/health';
 import { statusRoutes } from './routes/status';
 import { diseaseRoutes } from './routes/diseases';
 import { classificationRoutes } from './routes/classifications';
+import { diagnosisRoutes } from './routes/diagnoses';
 import { dashboardRoutes } from './routes/dashboard';
 import { authRoutes } from './routes/auth';
 
@@ -15,6 +16,7 @@ const app = new Elysia()
   .use(authRoutes)
   .use(diseaseRoutes)
   .use(classificationRoutes)
+  .use(diagnosisRoutes)
   .use(dashboardRoutes)
   .listen(env.port);