feat v1.29.0: 'new device' flag with a red dot

- auto devices/light groups appearing after install get a server-side 'new'
  flag (settings.new_device_ids) and a red dot top-right of the icon; opening
  the device's editor clears it for every client
- known_devices baseline seeded silently on first run — upgrades never flood
  the plan with dots; hand-made markers never flagged
- pure diffNewDevices + unit tests; backend schema; smoke_new_device.mjs;
  TESTING.md row

demo/smoke_new_device.mjs

@@ -0,0 +1,32 @@
+import { launch } from './serve.mjs';
+const { page, browser } = await launch();
+const res = await page.evaluate(async () => {
+  const out = {};
+  const c = window.__card;
+  const sr = () => c.shadowRoot || c.renderRoot;
+  // 1) первый запуск: базлайн засеян молча, точек нет
+  out.baselineSeeded = Array.isArray(c._serverCfg.settings.known_devices) && c._serverCfg.settings.known_devices.length > 0;
+  out.noDotsOnFirstRun = sr().querySelectorAll('.newdot').length === 0;
+  // 2) в HA появилось новое устройство
+  const h = { ...c.hass };
+  h.devices = { ...h.devices, d_new: { id: 'd_new', name: 'Brand new plug', model: 'Smart Plug', area_id: 'kitchen', identifiers: [['demo', 'd_new']] } };
+  h.entities = { ...h.entities, 'switch.newplug': { entity_id: 'switch.newplug', device_id: 'd_new', platform: 'demo' } };
+  h.states = { ...h.states, 'switch.newplug': { state: 'off', attributes: { friendly_name: 'Brand new plug' } } };
+  c.hass = h; await c.updateComplete; c.requestUpdate(); await c.updateComplete;
+  out.flagged = c._serverCfg.settings.new_device_ids?.includes('d_new');
+  out.dotShown = sr().querySelectorAll('.newdot').length === 1;
+  // 3) существующие не флагуются
+  out.onlyOne = (c._serverCfg.settings.new_device_ids || []).length === 1;
+  // 4) открытие редактора снимает флаг
+  const dev = c._devices.find((d) => d.id === 'd_new');
+  c._setMode('devices');
+  c._openMarkerDialog(dev); await c.updateComplete;
+  c._markerDialog = null; c._setMode('view'); await c.updateComplete;
+  out.ackCleared = !(c._serverCfg.settings.new_device_ids || []).includes('d_new');
+  out.dotGone = sr().querySelectorAll('.newdot').length === 0;
+  // 5) known растёт, повторно не флагуется
+  out.stillKnown = c._serverCfg.settings.known_devices.includes('d_new');
+  return out;
+});
+console.log(JSON.stringify(res, null, 1));
+await browser.close();