Add admin maintenance endpoints and file deletion functionality

- Introduced a new `/api/admin/maintenance` route for administrative maintenance tasks, requiring admin authorization.
- Implemented the `DeleteAsync` method in `IFileStorage` to allow for the deletion of files associated with closed support tickets.
- Updated API documentation to include details about the new maintenance operations and their effects on closed tickets.
- Enhanced frontend routing to include the new maintenance section in the admin panel, improving navigation for administrators.
- Added localization support for maintenance-related actions in both Russian and English.

backend/src/PnvPanel.Application/Admin/Maintenance/DeleteClosedTicketsCommand.cs

@@ -0,0 +1,8 @@
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Admin.Maintenance;
+
+/// <summary>Удаляет все тикеты в статусе Closed вместе с их перепиской и вложениями (в т.ч. файлами
+/// на диске). Value — число удалённых тикетов.</summary>
+public sealed record DeleteClosedTicketsCommand : ICommand<Result<int>>;

backend/src/PnvPanel.Application/Admin/Maintenance/DeleteClosedTicketsCommandHandler.cs

@@ -0,0 +1,69 @@
+using Microsoft.EntityFrameworkCore;
+using PnvPanel.Application.Auth;
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+using PnvPanel.Domain.Audit;
+using PnvPanel.Domain.Support;
+
+namespace PnvPanel.Application.Admin.Maintenance;
+
+public sealed class DeleteClosedTicketsCommandHandler(
+    IAppDbContext dbContext,
+    IFileStorage fileStorage,
+    ICurrentUser currentUser
+) : ICommandHandler<DeleteClosedTicketsCommand, Result<int>>
+{
+    public async Task<Result<int>> Handle(
+        DeleteClosedTicketsCommand command,
+        CancellationToken cancellationToken
+    )
+    {
+        if (currentUser.UserId is not { } adminId)
+            return Result.Failure<int>(AuthErrors.Unauthorized);
+
+        var ticketIds = await dbContext
+            .SupportTickets.AsNoTracking()
+            .Where(t => t.Status == TicketStatus.Closed)
+            .Select(t => t.Id)
+            .ToListAsync(cancellationToken);
+
+        if (ticketIds.Count == 0)
+            return Result.Success(0);
+
+        // Тикет/комментарий/вложение — плоские сущности без FK-каскада (см. SupportTicket), поэтому
+        // порядок удаления важен: вложения (+ файлы на диске) -> комментарии -> тикеты.
+        var comments = await dbContext
+            .TicketComments.Where(c => ticketIds.Contains(c.TicketId))
+            .ToListAsync(cancellationToken);
+        var commentIds = comments.Select(c => c.Id).ToList();
+
+        var attachments = await dbContext
+            .TicketAttachments.Where(a => commentIds.Contains(a.CommentId))
+            .ToListAsync(cancellationToken);
+
+        foreach (var attachment in attachments)
+            await fileStorage.DeleteAsync(attachment.StoredFileName, cancellationToken);
+
+        dbContext.TicketAttachments.RemoveRange(attachments);
+        dbContext.TicketComments.RemoveRange(comments);
+
+        var tickets = await dbContext
+            .SupportTickets.Where(t => ticketIds.Contains(t.Id))
+            .ToListAsync(cancellationToken);
+        dbContext.SupportTickets.RemoveRange(tickets);
+
+        dbContext.AuditLogs.Add(
+            AuditLog.Create(
+                adminId,
+                "ClosedTicketsCleanedUp",
+                "SupportTicket",
+                "bulk",
+                metadata: $"count={ticketIds.Count}",
+                AuditSource.Web
+            )
+        );
+
+        return Result.Success(ticketIds.Count);
+    }
+}

backend/src/PnvPanel.Application/Common/Interfaces/IFileStorage.cs

@@ -12,4 +12,7 @@ public interface IFileStorage
 
     /// <summary>Null, если файла с таким именем нет на диске (например, удалён вручную).</summary>
     Task<Stream?> OpenReadAsync(string storedFileName, CancellationToken cancellationToken);
+
+    /// <summary>Идемпотентно — отсутствие файла не ошибка (мог быть удалён вручную).</summary>
+    Task DeleteAsync(string storedFileName, CancellationToken cancellationToken);
 }