Background running for downloads/auto-download, library clipboard detect, updater auth + token

Closing the window no longer kills in-progress downloads, the library gains the
same copied-link suggestion the downloads tab has, and the in-app updater can now
authenticate to a sign-in-required Gitea.

Background / tray:
- The window's close handler now hides to the tray (instead of quitting) whenever
  a download is in flight, even if "Keep running in the tray" is off — quitting
  was killing the spawned yt-dlp processes. A one-time notification explains the
  app is still running. (download.ts exposes hasActiveDownloads().)
- tray.ts now falls back to an embedded icon when no build/icon.ico ships, so the
  tray actually appears — previously an empty icon meant the tray was skipped and
  a minimized window could be stranded with no way back.
- New "Start with Windows" setting (launchAtStartup) wired to
  app.setLoginItemSettings, synced at startup and on toggle. Useful with
  auto-download so watched channels stay current in the background.
- The "Keep running in the tray" hint now explains it also enables background
  auto-download of new uploads.

Library clipboard detection:
- Extracted the downloads tab's clipboard watcher into a shared useClipboardLink
  hook and used it in the library's add-source field, so a copied channel/playlist
  link is offered there too.

Updater fix (works on a private / sign-in-required instance):
- Added an optional updateToken setting. When set, the updater sends it as a Gitea
  Authorization header on the release check, the checksum fetch, and the installer
  download — so "Check for updates" works where anonymous access is blocked (the
  previous "could not reach the update server" case). Blank = anonymous, unchanged.
  No token is ever shipped; it's only ever sent to the host-pinned update host.
  Settings gains a masked "Update access token" field.

Typecheck clean; 187 tests pass; electron-vite build clean. New UI verified in the
browser preview (tray/startup toggles, token field, library copied-link banner).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/index.ts

@@ -1,4 +1,4 @@
-import { app, shell, BrowserWindow, ipcMain, dialog, clipboard, nativeTheme } from 'electron'
+import { app, shell, BrowserWindow, ipcMain, dialog, clipboard, nativeTheme, Notification } from 'electron'
 import { join, resolve } from 'path'
 import { electronApp, optimizer, is } from '@electron-toolkit/utils'
 import {
@@ -15,9 +15,15 @@ import { getYtdlpVersion, updateYtdlp, runStartupYtdlpAutoUpdate } from './ytdlp
 import { getFfmpegVersions } from './ffmpeg'
 import { checkForAppUpdate, downloadAppUpdate, runAppUpdate } from './updater'
 import { probeMedia } from './probe'
-import { startDownload, cancelDownload, pauseDownload, previewCommand } from './download'
+import {
+  startDownload,
+  cancelDownload,
+  pauseDownload,
+  previewCommand,
+  hasActiveDownloads
+} from './download'
 import { runTerminal, cancelTerminal } from './terminal'
-import { getSettings, setSettings, ensureMediaDirs } from './settings'
+import { getSettings, setSettings, ensureMediaDirs, applyLaunchAtStartup } from './settings'
 import { listHistory, addHistory, removeHistory, removeManyHistory, clearHistory } from './history'
 import { listTemplates, saveTemplate, removeTemplate } from './templates'
 import { setupPortableData } from './portable'
@@ -95,6 +101,19 @@ function getSystemThemeInfo(): SystemThemeInfo {
   }
 }
 
+// Tell the user (once per run) that closing the window left AeroFetch running so
+// an in-progress download could finish — shown only when they haven't already
+// opted into tray mode, so a window that "won't close" doesn't read as a bug.
+let notifiedBackground = false
+function notifyBackgroundOnce(): void {
+  if (notifiedBackground || !Notification.isSupported()) return
+  notifiedBackground = true
+  new Notification({
+    title: 'AeroFetch is still running',
+    body: 'Your download is finishing in the background. Use the tray icon to reopen or quit.'
+  }).show()
+}
+
 // Web permissions a download manager never needs. They're denied for the app
 // window as defence-in-depth (audit T6): even if the renderer were compromised
 // (e.g. XSS via remote video metadata) it can't open the camera/mic, read
@@ -137,12 +156,20 @@ function createWindow(): void {
     else win.show()
   })
 
-  // Minimize-to-tray: when enabled, closing the window hides it to the tray
-  // instead of quitting. A real quit (tray menu / before-quit) sets isQuitting().
+  // Closing the window hides to the tray (instead of quitting) when either the
+  // user opted into background mode, OR a download is in flight — quitting would
+  // kill the spawned yt-dlp processes and lose the download. A real quit (tray
+  // menu / before-quit) sets isQuitting() so this lets the close through.
   win.on('close', (e) => {
-    if (getSettings().minimizeToTray && !isQuitting()) {
+    if (isQuitting()) return
+    const downloadsRunning = hasActiveDownloads()
+    if (getSettings().minimizeToTray || downloadsRunning) {
       e.preventDefault()
       win.hide()
+      // If we're only staying alive because a download is running (the user
+      // didn't opt into tray mode), tell them once — otherwise a window that
+      // won't close looks like a bug.
+      if (downloadsRunning && !getSettings().minimizeToTray) notifyBackgroundOnce()
     }
   })
 
@@ -371,6 +398,10 @@ if (isPrimaryInstance) {
     // exist from first launch (downloads are routed into them by kind).
     ensureMediaDirs()
 
+    // Sync the Windows "run at sign-in" entry with the persisted setting, so it
+    // reflects the user's choice even if they changed it on another install.
+    applyLaunchAtStartup(getSettings().launchAtStartup)
+
     app.on('browser-window-created', (_, window) => {
       optimizer.watchWindowShortcuts(window)
     })