Corrige badge de mensagens nao lidas no chat web e desktop

- Web: markChatRead agora zera unreadByAgent na sessao ativa
- Desktop: usa unreadCount do backend ao inves de calcular localmente
- Backend: listMachineMessages retorna unreadCount da sessao
- Centraliza colunas da tabela de tickets do dispositivo

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

convex/liveChat.ts

@@ -467,7 +467,7 @@ export const listMachineMessages = query({
       .first()
 
     if (!session) {
-      return { messages: [], hasSession: false }
+      return { messages: [], hasSession: false, unreadCount: 0 }
     }
 
     // Aplicar limite (máximo 100 mensagens por chamada)
@@ -505,7 +505,7 @@ export const listMachineMessages = query({
       }
     })
 
-    return { messages: result, hasSession: true }
+    return { messages: result, hasSession: true, unreadCount: session.unreadByMachine ?? 0 }
   },
 })