test: add repository tests to improve coverage from 46.6% to 74%

New test files:
- custom_field_repository_test.go: 10 tests for CustomFieldRepository & UserCustomFieldValueRepository
- login_log_repository_test.go: 3 tests for ListCursor, ListByUserIDCursor, ListAllForExport
- operation_log_repository_test.go: 1 test for ListCursor
- role_repository_test.go: 2 tests for GetAncestorIDs, GetAncestors
- social_account_repository_test.go: 8 CRUD tests
- theme_repository_test.go: 10 tests for ThemeConfigRepository
- user_role_repository_test.go: 1 test for DeleteByUserAndRole

Modified test files:
- device_repository_test.go: Added ListAllCursor tests
- user_repository_test.go: Added AdvancedSearch tests
- webhook_repository_test.go: Added ListByCreatorPaginated test

Updated documentation with new coverage status.

internal/repository/operation_log_repository_test.go

@@ -0,0 +1,94 @@
+package repository
+
+import (
+	"context"
+	"fmt"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	_ "modernc.org/sqlite"
+	gormsqlite "gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+	"gorm.io/gorm/logger"
+
+	"github.com/user-management-system/internal/domain"
+	"github.com/user-management-system/internal/pagination"
+)
+
+var operationLogTestCounter int64
+
+func openOperationLogTestDB(t *testing.T) *gorm.DB {
+	t.Helper()
+
+	id := atomic.AddInt64(&operationLogTestCounter, 1)
+	dsn := fmt.Sprintf("file:operationlogtestdb%d?mode=memory&cache=private", id)
+
+	db, err := gorm.Open(gormsqlite.New(gormsqlite.Config{
+		DriverName: "sqlite",
+		DSN:        dsn,
+	}), &gorm.Config{
+		Logger: logger.Default.LogMode(logger.Silent),
+	})
+	if err != nil {
+		t.Fatalf("打开测试数据库失败: %v", err)
+	}
+
+	if err := db.AutoMigrate(&domain.OperationLog{}); err != nil {
+		t.Fatalf("数据库迁移失败: %v", err)
+	}
+	return db
+}
+
+func setupOperationLogTestDB(t *testing.T) *gorm.DB {
+	return openOperationLogTestDB(t)
+}
+
+func TestOperationLogRepository_ListCursor(t *testing.T) {
+	db := setupOperationLogTestDB(t)
+	repo := NewOperationLogRepository(db)
+	ctx := context.Background()
+
+	now := time.Now()
+	for i := 0; i < 5; i++ {
+		repo.Create(ctx, &domain.OperationLog{
+			UserID:         nil,
+			OperationType: "test",
+			OperationName:  "测试操作" + string(rune('0'+i)),
+			RequestMethod:  "GET",
+			RequestPath:    "/api/test",
+			ResponseStatus: 200,
+			IP:             "192.168.1." + string(rune('0'+i)),
+			CreatedAt:      now.Add(-time.Duration(i) * time.Minute),
+		})
+	}
+
+	// 第一次查询，获取前3个
+	logs, hasMore, err := repo.ListCursor(ctx, 3, nil)
+	if err != nil {
+		t.Fatalf("ListCursor() error = %v", err)
+	}
+	if len(logs) != 3 {
+		t.Errorf("len(logs) = %d, want 3", len(logs))
+	}
+	if !hasMore {
+		t.Error("hasMore should be true when more logs exist")
+	}
+
+	// 使用游标继续查询
+	lastLog := logs[len(logs)-1]
+	cursor := &pagination.Cursor{
+		LastID:    lastLog.ID,
+		LastValue: lastLog.CreatedAt,
+	}
+	logs2, hasMore2, err := repo.ListCursor(ctx, 3, cursor)
+	if err != nil {
+		t.Fatalf("ListCursor() error = %v", err)
+	}
+	if len(logs2) != 2 {
+		t.Errorf("len(logs2) = %d, want 2", len(logs2))
+	}
+	if hasMore2 {
+		t.Error("hasMore2 should be false")
+	}
+}