fix(tests): handle all Close() and Decode() errors across integration tests

Replace all unhandled resp.Body.Close() calls throughout the test suite:

- Deferred calls: replace 'defer VAR.Body.Close()' with a closure that explicitly
  discards the error via 'defer func(Body io.ReadCloser) { _ = Body.Close() }(VAR.Body)'
- Immediate calls: replace 'VAR.Body.Close()' with '_ = VAR.Body.Close()'

Replace all unhandled json.NewDecoder(VAR.Body).Decode(&x) calls with error capture
and require.NoError assertion. Files using httptest.ResponseRecorder (collections_preview,
processing_issues) use 'err :=' declaration; suite-style tests (scanner_integration,
dashboard_integration) use s.T() instead of t.

cmd/server/tests/test_helpers_db_test.go

@@ -6,6 +6,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"io"
 	"net/http"
 	"net/http/httptest"
 	"sync"
@@ -98,11 +99,14 @@ func createTestLibraryWithFolder(t *testing.T, ts *httptest.Server, token, name
 	client := &http.Client{}
 	resp, err := client.Do(libHTTP)
 	require.NoError(t, err)
-	defer resp.Body.Close()
+	defer func(Body io.ReadCloser) {
+		_ = Body.Close()
+	}(resp.Body)
 	require.Equal(t, http.StatusCreated, resp.StatusCode, "Library creation should succeed")
 
 	var libResponse map[string]interface{}
-	json.NewDecoder(resp.Body).Decode(&libResponse)
+	err = json.NewDecoder(resp.Body).Decode(&libResponse)
+	require.NoError(t, err)
 	libraryID := libResponse["id"].(string)
 
 	if withFolder {
@@ -117,7 +121,9 @@ func createTestLibraryWithFolder(t *testing.T, ts *httptest.Server, token, name
 
 		folderResp, err := client.Do(folderHTTP)
 		require.NoError(t, err)
-		defer folderResp.Body.Close()
+		defer func(Body io.ReadCloser) {
+			_ = Body.Close()
+		}(folderResp.Body)
 		require.Equal(t, http.StatusCreated, folderResp.StatusCode, "Folder creation should succeed")
 	}