feat: 实现租户列表查询接口

- 获取租户列表：GET /api/admin/v1/tenants
- 用于填充租户下拉选择器

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Infrastructure/TakeoutSaaS.Infrastructure/App/Repositories/EfTenantRepository.cs

@@ -34,4 +34,23 @@ public sealed class EfTenantRepository(TakeoutAdminDbContext context) : ITenantR
             .Where(x => tenantIds.Contains(x.Id))
             .ToListAsync(cancellationToken);
     }
+
+    /// <inheritdoc />
+    public async Task<IReadOnlyList<Tenant>> GetAllAsync(string? keyword, CancellationToken cancellationToken = default)
+    {
+        // 1. 构建基础查询
+        var query = context.Tenants
+            .AsNoTracking()
+            .Where(x => x.DeletedAt == null);
+
+        // 2. 应用关键字过滤
+        if (!string.IsNullOrWhiteSpace(keyword))
+        {
+            var normalized = keyword.Trim();
+            query = query.Where(x => x.Name.Contains(normalized) || x.Code.Contains(normalized));
+        }
+
+        // 3. 返回列表
+        return await query.OrderBy(x => x.Code).ToListAsync(cancellationToken);
+    }
 }