Fix unread badge - increment unreadByMachine when agent sends message

The unreadByMachine counter was never being incremented when agents sent
chat messages, causing the badge to always show 0. Now when an agent
(ADMIN/MANAGER/AGENT) posts a message to a ticket with an active chat
session, the counter is incremented properly.

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

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

convex/tickets.ts

@@ -3257,6 +3257,23 @@ export const postChatMessage = mutation({
 
     await ctx.db.patch(ticketId, { updatedAt: now })
 
+    // Se o autor for um agente (ADMIN, MANAGER, AGENT), incrementar unreadByMachine na sessao de chat ativa
+    const actorRole = participant.role?.toUpperCase() ?? ""
+    if (["ADMIN", "MANAGER", "AGENT"].includes(actorRole)) {
+      const activeSession = await ctx.db
+        .query("liveChatSessions")
+        .withIndex("by_ticket", (q) => q.eq("ticketId", ticketId))
+        .filter((q) => q.eq(q.field("status"), "ACTIVE"))
+        .first()
+
+      if (activeSession) {
+        await ctx.db.patch(activeSession._id, {
+          unreadByMachine: (activeSession.unreadByMachine ?? 0) + 1,
+          lastActivityAt: now,
+        })
+      }
+    }
+
     return { ok: true, messageId }
   },
 })