游标分页优化

# Conflicts:
#	src/Jiaowu.Api/Controllers/TuitionController.cs
#	src/Jiaowu.Api/Infrastructure/Persistence/Migrations/MySql/20260822090000_CampusRegistrationPayments.cs
#	tests/Jiaowu.Api.Tests/MySqlMigrationTests.cs
#	web/src/views/CampusWalletManagementView.vue
#	web/src/views/TuitionView.vue

src/Jiaowu.Api/Contracts/CursorToken.cs

@@ -0,0 +1,29 @@
+using System.Text;
+using System.Text.Json;
+
+namespace Jiaowu.Api.Contracts;
+
+/// <summary>Encodes endpoint-specific keyset values without exposing a query offset.</summary>
+public static class CursorToken
+{
+    private static readonly JsonSerializerOptions Options = new(JsonSerializerDefaults.Web);
+
+    public static string Encode<T>(T value) =>
+        Convert.ToBase64String(Encoding.UTF8.GetBytes(JsonSerializer.Serialize(value, Options)))
+            .TrimEnd('=').Replace('+', '-').Replace('/', '_');
+
+    public static bool TryDecode<T>(string? token, out T? value)
+    {
+        value = default;
+        if (string.IsNullOrWhiteSpace(token)) return true;
+        try
+        {
+            var normalized = token.Replace('-', '+').Replace('_', '/');
+            normalized = normalized.PadRight(normalized.Length + (4 - normalized.Length % 4) % 4, '=');
+            value = JsonSerializer.Deserialize<T>(Encoding.UTF8.GetString(Convert.FromBase64String(normalized)), Options);
+            return value is not null;
+        }
+        catch (JsonException) { return false; }
+        catch (FormatException) { return false; }
+    }
+}

src/Jiaowu.Api/Contracts/PagedResult.cs

@@ -1,5 +1,20 @@
 namespace Jiaowu.Api.Contracts;
 
+/// <summary>
+/// A forward-only keyset page.  <see cref="NextCursor"/> is opaque to clients and
+/// must be sent back unchanged as the <c>cursor</c> query parameter.
+/// </summary>
+public sealed record CursorPagedResult<T>(
+    IReadOnlyCollection<T> Items,
+    string? NextCursor,
+    bool HasMore,
+    int PageSize,
+    int? Total = null);
+
+/// <summary>
+/// Legacy offset-page response. New list endpoints must use
+/// <see cref="CursorPagedResult{T}"/> instead.
+/// </summary>
 public sealed record PagedResult<T>(
     IReadOnlyCollection<T> Items,
     int Total,

src/Jiaowu.Api/Controllers/AppUpdatesController.cs

@@ -113,15 +113,17 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
 
     [Authorize(Roles = SystemRoles.SuperAdmin)]
     [HttpGet("releases")]
-    public async Task<ActionResult<PagedResult<AppUpdateReleaseItem>>> GetReleases(
-        [FromQuery] int page = 1,
+    public async Task<ActionResult<CursorPagedResult<AppUpdateReleaseItem>>> GetReleases(
+        [FromQuery] string? cursor = null,
         [FromQuery] int pageSize = 20,
         [FromQuery] string? platform = null,
         [FromQuery] string? channel = null,
         CancellationToken cancellationToken = default)
     {
-        if (page < 1 || pageSize is < 1 or > 100)
-            return ValidationProblem("页码必须大于零，每页数量必须在 1 到 100 之间。");
+        if (pageSize is < 1 or > 100)
+            return ValidationProblem("每批数量必须在 1 到 100 之间。");
+        if (!CursorToken.TryDecode<ReleaseCursor>(cursor, out var after))
+            return BadRequest("更新包游标无效。");
 
         var query = db.AppUpdateReleases.AsNoTracking().AsQueryable();
         if (!string.IsNullOrWhiteSpace(platform))
@@ -137,11 +139,21 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
             query = query.Where(x => x.Channel == parsedChannel);
         }
 
-        var total = await query.CountAsync(cancellationToken);
-        var rows = await query
+        if (after is not null)
+        {
+            query = query.Where(x => (x.PublishedAt ?? x.CreatedAt) < after.SortAt ||
+                (x.PublishedAt ?? x.CreatedAt) == after.SortAt && x.Id.CompareTo(after.Id) < 0);
+        }
+        var keys = await query
             .OrderByDescending(x => x.PublishedAt ?? x.CreatedAt)
-            .Skip((page - 1) * pageSize)
-            .Take(pageSize)
+            .ThenByDescending(x => x.Id)
+            .Take(pageSize + 1)
+            .Select(x => new { x.Id, SortAt = x.PublishedAt ?? x.CreatedAt })
+            .ToArrayAsync(cancellationToken);
+        var hasMore = keys.Length > pageSize;
+        var pageIds = keys.Take(pageSize).Select(x => x.Id).ToArray();
+        var rows = await query.WhereIn(pageIds, x => x.Id)
+            .OrderByDescending(x => x.PublishedAt ?? x.CreatedAt).ThenByDescending(x => x.Id)
             .Select(x => new AppUpdateReleaseItem(
                 x.Id,
                 x.Platform,
@@ -158,13 +170,16 @@ public sealed partial class AppUpdatesController(AppDbContext db) : ControllerBa
                 x.PublishedByUserName,
                 x.PublishedAt))
             .ToArrayAsync(cancellationToken);
-        return Ok(new PagedResult<AppUpdateReleaseItem>(
+        var last = keys.Take(pageSize).LastOrDefault();
+        return Ok(new CursorPagedResult<AppUpdateReleaseItem>(
             rows,
-            total,
-            page,
+            hasMore && last is not null ? CursorToken.Encode(new ReleaseCursor(last.SortAt, last.Id)) : null,
+            hasMore,
             pageSize));
     }
 
+    private sealed record ReleaseCursor(DateTime SortAt, Guid Id);
+
     [Authorize(Roles = SystemRoles.SuperAdmin)]
     [Consumes("multipart/form-data")]
     [RequestSizeLimit(MaximumBundleBytes + 1024 * 1024)]