test: update Bruno test data for media items

Update Bruno API test collections with latest test data:

Bookhoard.yml environment:
- Update media_item_id to current database value after recent
  database recreation/schema updates

Create Media Rating test:
- Change test rating from 8 to 7 to test different rating value
  for validation

These are test infrastructure updates only, no application code changes.

bruno/media-items/Create Media Rating.yml

@@ -13,7 +13,7 @@ http:
     type: json
     data: |-
       {
-        "rating": 8
+        "rating": 7
       }
   auth: inherit