fix: 修复公告模块核心问题并完善功能

主要修复内容：
1. 修复 RowVersion 并发控制
   - 配置 EF Core RowVersion 映射为 bytea 类型
   - 添加 PostgreSQL 触发器自动生成 RowVersion
   - 在更新/发布/撤销操作中添加 RowVersion 校验
   - 移除 Application 层对 EF Core 的直接依赖

2. 修复 API 路由和校验问题
   - 添加平台公告列表路由的版本化别名
   - 租户公告接口添加 X-Tenant-Id 必填校验，返回 400
   - 生效时间校验返回 422 而非 500
   - 修复 FluentValidation 异常命名冲突

3. 实现关键词搜索功能
   - 在查询参数中添加 keyword 字段
   - 使用 PostgreSQL ILIKE 实现大小写不敏感搜索
   - 支持标题和内容字段的模糊匹配

4. 数据库迁移
   - 新增 RowVersion 触发器迁移文件
   - 回填现有公告记录的 RowVersion

src/Application/TakeoutSaaS.Application/App/Tenants/Handlers/GetTenantsAnnouncementsQueryHandler.cs

@@ -44,6 +44,7 @@ public sealed class GetTenantsAnnouncementsQueryHandler(
         // 1. 优化的数据库查询：应用排序和限制
         var announcements = await announcementRepository.SearchAsync(
             tenantId,
+            request.Keyword,
             request.Status,
             request.AnnouncementType,
             request.IsActive,

src/Application/TakeoutSaaS.Application/App/Tenants/Handlers/PublishAnnouncementCommandHandler.cs

@@ -23,6 +23,11 @@ public sealed class PublishAnnouncementCommandHandler(
     /// <inheritdoc />
     public async Task<TenantAnnouncementDto?> Handle(PublishAnnouncementCommand request, CancellationToken cancellationToken)
     {
+        if (request.RowVersion == null || request.RowVersion.Length == 0)
+        {
+            throw new BusinessException(ErrorCodes.ValidationFailed, "RowVersion 不能为空");
+        }
+
         // 1. 查询公告
         var tenantId = tenantProvider.GetCurrentTenantId();
         var announcement = await announcementRepository.FindByIdAsync(tenantId, request.AnnouncementId, cancellationToken);

src/Application/TakeoutSaaS.Application/App/Tenants/Handlers/RevokeAnnouncementCommandHandler.cs

@@ -23,6 +23,11 @@ public sealed class RevokeAnnouncementCommandHandler(
     /// <inheritdoc />
     public async Task<TenantAnnouncementDto?> Handle(RevokeAnnouncementCommand request, CancellationToken cancellationToken)
     {
+        if (request.RowVersion == null || request.RowVersion.Length == 0)
+        {
+            throw new BusinessException(ErrorCodes.ValidationFailed, "RowVersion 不能为空");
+        }
+
         // 1. 查询公告
         var tenantId = tenantProvider.GetCurrentTenantId();
         var announcement = await announcementRepository.FindByIdAsync(tenantId, request.AnnouncementId, cancellationToken);

src/Application/TakeoutSaaS.Application/App/Tenants/Handlers/UpdateTenantAnnouncementCommandHandler.cs

@@ -22,6 +22,11 @@ public sealed class UpdateTenantAnnouncementCommandHandler(ITenantAnnouncementRe
             throw new BusinessException(ErrorCodes.ValidationFailed, "公告标题和内容不能为空");
         }
 
+        if (request.RowVersion == null || request.RowVersion.Length == 0)
+        {
+            throw new BusinessException(ErrorCodes.ValidationFailed, "RowVersion 不能为空");
+        }
+
         // 2. 查询公告
         var announcement = await announcementRepository.FindByIdAsync(request.TenantId, request.AnnouncementId, cancellationToken);
         if (announcement == null)