Add IPTV playlist functionality and enhance streaming endpoints

Implemented a new endpoint for downloading the IPTV playlist, allowing users to access a comprehensive M3U file containing all channels and program guides. Updated the StreamingEndpoints to support token validation for both cookie and query parameters, ensuring secure access for external IPTV players. Enhanced the AirPage component to include a download button for the IPTV playlist, with appropriate user feedback on success or failure. Updated localization strings to reflect new features and instructions for users.

frontend/src/shared/lib/locales/en.ts

@@ -66,6 +66,11 @@ export const en = {
     offlineHint: 'No schedule or content yet. Check back later.',
     retry: 'Retry',
     numbersHint: '↑ / ↓ — switch channels by number',
+    iptv: 'IPTV playlist',
+    iptvHint:
+      'An M3U with every channel and the programme guide — for VLC, TiviMate and the like. Access to the air is baked into the file itself: do not share it.',
+    iptvDone: 'Playlist downloaded. The file grants access to the air — do not pass it on.',
+    iptvFailed: 'Could not build the playlist',
   },
   settings: {
     title: 'Account settings',