Fix learning hub upload: ensure mopc-learning bucket exists

The getUploadUrl procedure generated a presigned PUT URL without first
checking that the mopc-learning bucket exists, causing all uploads to fail.

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

src/server/routers/learningResource.ts

@@ -6,7 +6,7 @@ import {
   protectedProcedure,
   adminProcedure,
 } from '../trpc'
-import { getPresignedUrl } from '@/lib/minio'
+import { getPresignedUrl, ensureBucket } from '@/lib/minio'
 import { logAudit } from '../utils/audit'
 
 // Bucket for learning resources
@@ -415,6 +415,7 @@ export const learningResourceRouter = router({
       const sanitizedName = input.fileName.replace(/[^a-zA-Z0-9.-]/g, '_')
       const objectKey = `resources/${timestamp}-${sanitizedName}`
 
+      await ensureBucket(LEARNING_BUCKET)
       const url = await getPresignedUrl(LEARNING_BUCKET, objectKey, 'PUT', 3600)
 
       return {