Add header quick links with CRUD management and icon enhancements

- Add LinkConfig model and links field to settings
- Add CRUD API endpoints for links (list/create/update/delete)
- Add Links management tab in WebUI with add/edit/delete dialogs
- Add live icon preview in Link and Script dialog forms
- Show MDI icons inline in Quick Actions cards, Scripts table, Links table
- Add broadcast_links_changed WebSocket event for live updates
- Add EN/RU translations for all links management strings

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

media_server/services/websocket_manager.py

@@ -77,6 +77,12 @@ class ConnectionManager:
         await self.broadcast(message)
         logger.info("Broadcast sent: scripts_changed")
 
+    async def broadcast_links_changed(self) -> None:
+        """Notify all connected clients that links have changed."""
+        message = {"type": "links_changed", "data": {}}
+        await self.broadcast(message)
+        logger.info("Broadcast sent: links_changed")
+
     def status_changed(
         self, old: dict[str, Any] | None, new: dict[str, Any]
     ) -> bool: