feat(P3.T4): ensure device row + revoke-realtime + revokedRemotely flag

apps/desktop/src/lib/deviceRowId.ts

@@ -0,0 +1,30 @@
+// localStorage key for "the devices.id row that belongs to THIS install".
+// Reset on memory-wipe (NOT preserved) — a wiped install is conceptually a
+// fresh install, so registering a new row is correct.
+
+const KEY = 'chatapp.deviceRowId.v1';
+
+export function getDeviceRowId(): string | null {
+  try {
+    const v = window.localStorage.getItem(KEY);
+    return v && v.length > 0 ? v : null;
+  } catch {
+    return null;
+  }
+}
+
+export function setDeviceRowId(id: string): void {
+  try {
+    window.localStorage.setItem(KEY, id);
+  } catch {
+    /* quota */
+  }
+}
+
+export function clearDeviceRowId(): void {
+  try {
+    window.localStorage.removeItem(KEY);
+  } catch {
+    /* no-op */
+  }
+}