feat: multi-media attachments, linkify URLs, shared MessageMediaGrid

- Add media_items array support to ticket messages (types, API clients)
- Create shared MessageMediaGrid component with photo grid, fullscreen
  viewer, keyboard nav, video/document rendering
- Replace per-page AdminMessageMedia/MessageMedia with MessageMediaGrid
- Add linkifyText util (DOMPurify-sanitized) for auto-linking URLs
- Support multi-file upload (up to 10) in AdminTickets and Support pages
- Remove unused ticketsApi import from AdminUserDetail

src/types/index.ts

@@ -473,6 +473,12 @@ export interface ReferralTerms {
 }
 
 // Ticket types
+export interface TicketMediaItem {
+  type: 'photo' | 'video' | 'document';
+  file_id: string;
+  caption?: string | null;
+}
+
 export interface TicketMessage {
   id: number;
   message_text: string;
@@ -481,6 +487,7 @@ export interface TicketMessage {
   media_type: string | null;
   media_file_id: string | null;
   media_caption: string | null;
+  media_items?: TicketMediaItem[] | null;
   created_at: string;
 }