Implement extension request and gift functionalities in billing system

- Added new endpoints for creating and managing extension requests, allowing users to request billing period extensions.
- Implemented admin approval processes for extension requests via Telegram, including inline buttons for approval and rejection.
- Introduced a gifting feature for admins to grant additional billing days directly to users without a request.
- Updated the support ticket model to accommodate extension requests and their associated properties.
- Enhanced the Telegram notifier to inform admins of new extension requests and notify users of approval or rejection.
- Updated frontend components to support the new extension request and gifting functionalities, including user interfaces for managing these features.
- Revised API documentation to reflect the new endpoints and their usage in the billing context.

frontend/src/features/support/TicketDetailDialog.tsx

@@ -75,6 +75,12 @@ export function TicketDetailDialog({ ticketId, onOpenChange }: { ticketId: strin
               </div>
             )}
 
+            {data.type === 'ExtensionRequest' && (
+              <div className="rounded-md border border-border p-3 text-sm">
+                {t('support.requestedExtension', { days: data.requestedDays })}
+              </div>
+            )}
+
             <div className="flex flex-col gap-3">
               {data.comments.map((comment) => (
                 <div key={comment.id} className="rounded-md border border-border p-3">