feat(P3.T3): app:hostname IPC for device-name default

apps/desktop/electron/ipc-types.ts

@@ -114,6 +114,11 @@ export const CHANNELS = {
   // timeout, whichever comes first).
   /** Main → renderer: about to quit. Renderer wipes, then resolves. */
   APP_WIPE_BEFORE_QUIT: 'app:wipe-before-quit',
+
+  // OS hostname — returns the machine hostname via Node's `os.hostname()`.
+  // Used by AuthContext on first launch to populate the `devices` row with
+  // a human-readable default device name. Returns null on failure.
+  APP_HOSTNAME: 'app:hostname',
 } as const;
 
 // ---- Screen sources ------------------------------------------------------

apps/desktop/electron/main.ts

@@ -12,6 +12,7 @@ import { fileURLToPath } from 'node:url';
 
 import { CHANNELS } from './ipc-types';
 import { register as registerAudioLoopback } from './modules/audio-loopback';
+import { register as registerAppHostname } from './modules/app-hostname';
 import { register as registerAutostart } from './modules/autostart';
 import { register as registerFsScoped } from './modules/fs-scoped';
 import { register as registerNotifications } from './modules/notifications';
@@ -254,6 +255,7 @@ if (!gotLock) {
     registerFsScoped();
     registerSql();
     registerAutostart();
+    registerAppHostname();
 
     // Window-dependent registrars — only call once mainWindow exists so
     // event emitters have somewhere to send.

apps/desktop/electron/modules/app-hostname.ts

@@ -0,0 +1,21 @@
+// app:hostname adapter — returns the OS hostname via Node's `os.hostname()`.
+// The renderer has no Node access (contextIsolation is ON), so it must ask
+// main for this value. Used by AuthContext on first launch to populate the
+// `devices` row with a human-readable default device name.
+
+import os from 'node:os';
+
+import { ipcMain } from 'electron';
+
+import { CHANNELS } from '../ipc-types';
+
+export function register(): void {
+  ipcMain.handle(CHANNELS.APP_HOSTNAME, (): string | null => {
+    try {
+      const h = os.hostname();
+      return typeof h === 'string' && h.length > 0 ? h : null;
+    } catch {
+      return null;
+    }
+  });
+}

apps/desktop/electron/preload-types.d.ts

@@ -99,6 +99,13 @@ export interface ElectronAPI {
   /** Subscribe to the main-process pre-quit notification. Used by the
    *  "Cache beim Schließen leeren" Settings toggle. */
   onWipeBeforeQuit: (cb: () => Promise<void>) => () => void;
+
+  /** Returns the OS hostname (via Node's `os.hostname()`). Used by
+   *  AuthContext on first launch to populate the `devices` row with a
+   *  human-readable default device name. Optional: always feature-check
+   *  via `typeof window.electronAPI?.getHostname === 'function'` because
+   *  the web build has no preload bridge. */
+  getHostname?: () => Promise<string | null>;
 }
 
 declare global {

apps/desktop/electron/preload.ts

@@ -160,6 +160,9 @@ const api = {
   setFullscreen: (enabled: boolean): Promise<void> =>
     ipcRenderer.invoke(CHANNELS.WINDOW_SET_FULLSCREEN, enabled),
 
+  // OS hostname ------------------------------------------------------------
+  getHostname: (): Promise<string | null> => ipcRenderer.invoke(CHANNELS.APP_HOSTNAME),
+
   // Wipe-on-close ----------------------------------------------------------
   // Subscribe to the main-process pre-quit notification. The renderer's
   // callback does the actual wipe (memoryWipe.ts) and resolves; we ack