Implement support ticket system with role request and bug report functionalities

- Introduced a new support ticket system allowing users to submit bug reports and role requests.
- Implemented endpoints for creating, updating, and managing support tickets, including file attachments.
- Enhanced Telegram bot integration to handle role requests directly within the bot, enabling admins to approve or reject requests without accessing the website.
- Updated database schema to include support ticket entities and their relationships.
- Improved API documentation to reflect new support ticket endpoints and their usage.
- Added necessary localization for support ticket features in both Russian and English.

backend/src/PnvPanel.Application/Support/ListSelectableRoles/ListSelectableRolesQueryHandler.cs

@@ -0,0 +1,21 @@
+using PnvPanel.Application.Common.Interfaces;
+using PnvPanel.Application.Common.Messaging;
+using PnvPanel.Application.Common.Models;
+
+namespace PnvPanel.Application.Support.ListSelectableRoles;
+
+public sealed class ListSelectableRolesQueryHandler(IRoleService roleService)
+    : IQueryHandler<ListSelectableRolesQuery, Result<IReadOnlyList<RoleDto>>>
+{
+    // Совпадает со значением Infrastructure.Identity.RoleNames.Admin — см. пояснение в
+    // CreateRoleRequestTicketCommandHandler (Application не может ссылаться на Infrastructure).
+    private const string AdminRoleName = "admin";
+
+    public async Task<Result<IReadOnlyList<RoleDto>>> Handle(ListSelectableRolesQuery query, CancellationToken cancellationToken)
+    {
+        var roles = await roleService.ListRolesAsync(cancellationToken);
+        var selectable = roles.Where(r => !r.Name.Equals(AdminRoleName, StringComparison.OrdinalIgnoreCase)).ToList();
+
+        return Result.Success<IReadOnlyList<RoleDto>>(selectable);
+    }
+}