test: update test files to use @tests.bookhoard.internal domain

Update email domain in remaining test files:
- device_cap_test.go
- device_test.go
- queue_test.go
- refresh_token_test.go
- seven_day_session_test.go

All test files now consistently use the dedicated test domain
to prevent conflicts with real user data.

cmd/server/tests/seven_day_session_test.go

@@ -24,7 +24,7 @@ func TestSevenDaySession(t *testing.T) {
 
 	t.Run("Login returns 7-day session", func(t *testing.T) {
 		loginReq := map[string]string{
-			"login":    "testuser@example.com",
+			"login":    "testuser@tests.bookhoard.internal",
 			"password": "Test@Pass123!",
 		}
 		body, _ := json.Marshal(loginReq)
@@ -70,7 +70,7 @@ func TestSevenDaySession(t *testing.T) {
 	t.Run("Refresh token returns 7-day access token", func(t *testing.T) {
 		// First login to get refresh token
 		loginReq := map[string]string{
-			"login":    "testuser@example.com",
+			"login":    "testuser@tests.bookhoard.internal",
 			"password": "Test@Pass123!",
 		}
 		loginBody, _ := json.Marshal(loginReq)
@@ -123,7 +123,7 @@ func TestSevenDaySession(t *testing.T) {
 
 	t.Run("JWT token has 7-day expiration claim", func(t *testing.T) {
 		loginReq := map[string]string{
-			"login":    "testuser@example.com",
+			"login":    "testuser@tests.bookhoard.internal",
 			"password": "Test@Pass123!",
 		}
 		body, _ := json.Marshal(loginReq)
@@ -267,7 +267,7 @@ func TestNoClientSideCookies(t *testing.T) {
 	t.Run("Login does not set document.cookie", func(t *testing.T) {
 		// Use the standard test user
 		loginData := url.Values{}
-		loginData.Set("login", "testuser@example.com")
+		loginData.Set("login", "testuser@tests.bookhoard.internal")
 		loginData.Set("password", "Test@Pass123!")
 
 		loginReq, err := http.NewRequest("POST", setup.Server.URL+"/api/auth/login", strings.NewReader(loginData.Encode()))