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.Api/Endpoints/AdminMaintenanceEndpoints.cs

@@ -0,0 +1,36 @@
+using PnvPanel.Api.Common;
+using PnvPanel.Application.Admin.Maintenance;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Infrastructure.Identity;
+
+namespace PnvPanel.Api.Endpoints;
+
+public static class AdminMaintenanceEndpoints
+{
+    public static IEndpointRouteBuilder MapAdminMaintenanceEndpoints(this IEndpointRouteBuilder app)
+    {
+        var admin = app.MapGroup("/api/admin/maintenance")
+            .WithTags("Admin.Maintenance")
+            .RequireAuthorization(policy => policy.RequireRole(RoleNames.Admin));
+
+        admin
+            .MapDelete("/tickets/closed", DeleteClosedTickets)
+            .Produces<DeleteClosedTicketsResponseDto>();
+
+        return app;
+    }
+
+    private static async Task<IResult> DeleteClosedTickets(
+        ISender sender,
+        CancellationToken cancellationToken
+    )
+    {
+        var result = await sender.Send(new DeleteClosedTicketsCommand(), cancellationToken);
+        if (!result.IsSuccess)
+            return result.ToHttpResult();
+
+        return Results.Ok(new DeleteClosedTicketsResponseDto(result.Value));
+    }
+}
+
+public sealed record DeleteClosedTicketsResponseDto(int DeletedCount);

backend/src/PnvPanel.Api/Program.cs

@@ -191,6 +191,7 @@ app.MapAdminAppEndpoints();
 app.MapAdminNewsEndpoints();
 app.MapSupportEndpoints();
 app.MapAdminSupportEndpoints();
+app.MapAdminMaintenanceEndpoints();
 app.MapTelegramEndpoints();
 
 app.MapHub<PanelHub>("/hubs/panel");