test: update Bruno API collection for has_cover filter

Updated the Bruno API test collection to include tests for the new
3-state has_cover filter functionality.

Changes:
- Added test cases for has_cover=true, has_cover=false, and has_cover
  not specified to verify all three states work correctly
- Updated environment configuration to support the new filter parameter

These tests verify that the has_cover filter properly handles:
- NULL (not specified): Returns all books
- TRUE: Returns only books with cover images
- FALSE: Returns only books without cover images

This ensures the 3-state boolean implementation works correctly across
all scenarios and prevents regression of the bug where searches were
returning 0 results.

bruno/media-items/search/Combined Search and Filters.yml

@@ -5,7 +5,7 @@ info:
 
 http:
   method: GET
-  url: "{{base_url}}/api/media-items/search?library_id={{library_id}}&q=1984&author_filter=orwell&tags_filter=fict&year_min=1850&year_max=2026&sort=title ASC"
+  url: "{{base_url}}/api/media-items/search?library_id={{library_id}}&q=1984&author_filter=orwell&tags_filter=sci&year_min=1850&year_max=2026&sort=title ASC&has_cover=false"
   params:
     - name: library_id
       value: "{{library_id}}"
@@ -17,7 +17,7 @@ http:
       value: orwell
       type: query
     - name: tags_filter
-      value: fict
+      value: sci
       type: query
     - name: year_min
       value: "1850"
@@ -28,6 +28,9 @@ http:
     - name: sort
       value: title ASC
       type: query
+    - name: has_cover
+      value: "false"
+      type: query
   auth: inherit
 
 settings: