[feat](client): make delivery durable with an offline check-in and ack queue

The server ledger is cleared by an explicit ack, never by the check-in response, so a dismissal that cannot reach the service must be persisted and retried or the device rings again later. Add a durable pending-ack queue (404 means the alert ended: settled, drop it), map the 409 ERR_ALARM_TRIGGERED_OFFLINE check-in into a normal trigger for the same takeover, and make a 404 an ending rather than a missed alarm. This also carries the expiry/endings state the screens render.

__tests__/dismissContract.test.ts

@@ -0,0 +1,45 @@
+export {};
+
+/**
+ * Dismiss must silence the phone locally, first, without the owner.
+ *
+ * Source contract: JSX/native playback can't be executed headlessly here, so we
+ * pin the order the code depends on — `stopAlarm()` before any server call or
+ * event clearing in the acknowledge path — and that playback has no timer that
+ * could silence it "by itself".
+ */
+declare const __dirname: string;
+const fs: { readFileSync(p: string, enc: string): string } = jest.requireActual('fs');
+const path: { join(...parts: string[]): string } = jest.requireActual('path');
+
+const screen = fs.readFileSync(
+  path.join(__dirname, '..', 'src', 'screens', 'LiveAlarmScreen.tsx'),
+  'utf8',
+);
+const nativeTs = fs.readFileSync(
+  path.join(__dirname, '..', 'src', 'services', 'alarmNative.ts'),
+  'utf8',
+);
+
+describe('local dismiss contract', () => {
+  it('silences first and only then drops the live event', () => {
+    const ackAt = screen.indexOf('const ack = useCallback');
+    expect(ackAt).toBeGreaterThan(-1);
+    const ack = screen.slice(ackAt, ackAt + 900);
+    expect(ack.indexOf('await stopAlarm()')).toBeGreaterThan(-1);
+    expect(ack.indexOf('await stopAlarm()')).toBeLessThan(ack.indexOf('clearLiveEvent()'));
+  });
+
+  it('stops both audio and vibration through the native bridge', () => {
+    expect(nativeTs).toContain('stopAlarm');
+    expect(nativeTs).toContain('AlarmModule');
+  });
+
+  it('does not schedule its own auto-stop in JS', () => {
+    expect(screen).not.toMatch(/autoStop/i);
+    // The 1 s interval is the displayed count-up only; it must not stop audio.
+    const countUp = screen.slice(screen.indexOf('The count-up ticks'), screen.indexOf('The count-up ticks') + 300);
+    expect(countUp).toContain('setInterval');
+    expect(countUp).not.toContain('stopAlarm');
+  });
+});