fix(middleware): Correct rate limit header type conversion

cmd/server/tests/kobo_test.go

@@ -4,10 +4,21 @@ import (
 	"bookhoard/internal/handlers"
 	"bytes"
 	"encoding/json"
+	"fmt"
+	"log"
 	"net/http"
 	"net/http/httptest"
 	"testing"
 
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"bookhoard/internal/config"
+	"bookhoard/internal/database"
+	"bookhoard/internal/middleware"
+	"bookhoard/internal/router"
+	"bookhoard/internal/services"
+	"bookhoard/internal/sync"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -24,9 +35,25 @@ func TestKoboInitialization(t *testing.T) {
 	_ = getTestUserID(t, db)
 	_ = createTestMediaItemID(t, ts, token)
 
+	log.Printf("[DEBUG] Kobo test setup: creating device and media")
+
 	t.Run("successful initialization", func(t *testing.T) {
-		req, _ := http.NewRequest("GET", ts.URL+"/api/sync/kobo/test-token/v1/initialization", nil)
-		req.Header.Set("Authorization", "Bearer test-auth-token")
+		// Create Kobo device using TestDeviceSetup for proper authentication
+		deviceSetup := setupTestDevice(t, ts, db)
+		koboDevice := deviceSetup.CreateDevice(t, "Test Kobo", "kobo", "kobo-clara-test")
+
+		req, _ := http.NewRequest("GET", ts.URL+"/api/sync/kobo/v1/initialization", nil)
+		req.Header.Set("Authorization", "Bearer "+koboDevice.AuthToken)
+		req.Header.Set("x-kobo-device", fmt.Sprintf(`{"DeviceId":"%s","Model":"Kobo Clara","SerialNumber":"%s"}`, 
+			koboDevice.ID.String(), koboDevice.Identifier))
+
+		client := &http.Client{}
+		resp, err := client.Do(req)
+		require.NoError(t, err)
+		defer resp.Body.Close()
+
+		assert.Equal(t, http.StatusOK, resp.StatusCode)
+	})
 
 		client := &http.Client{}
 		resp, err := client.Do(req)