fix: align ticket timers to server clock

tests/ticket-timer.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vitest"
-import { reconcileLocalSessionStart } from "@/components/tickets/ticket-timer.utils"
+import { deriveServerOffset, reconcileLocalSessionStart, toServerTimestamp } from "@/components/tickets/ticket-timer.utils"
 
 describe("reconcileLocalSessionStart", () => {
   it("usa o timestamp remoto quando não há marcador local", () => {
@@ -34,3 +34,26 @@ describe("reconcileLocalSessionStart", () => {
     expect(result).toEqual({ localStart: 4_000, origin: "remote" })
   })
 })
+
+describe("deriveServerOffset", () => {
+  it("calcula deslocamento simples entre relógios", () => {
+    const offset = deriveServerOffset({ currentOffset: 0, localNow: 1_700_000, serverNow: 1_699_000 })
+    expect(offset).toBe(1_000)
+  })
+
+  it("ignora serverNow inválido", () => {
+    const offset = deriveServerOffset({ currentOffset: 500, localNow: 2_000_000, serverNow: Number.NaN })
+    expect(offset).toBe(500)
+  })
+
+  it("aceita saltos grandes quando necessário", () => {
+    const offset = deriveServerOffset({ currentOffset: 500, localNow: 2_000_000, serverNow: 1_000_000 })
+    expect(offset).toBe(1_000_000)
+  })
+})
+
+describe("toServerTimestamp", () => {
+  it("aplica offset corretamente", () => {
+    expect(toServerTimestamp(1_000_000, 1_500)).toBe(998_500)
+  })
+})