feat(updater): nightly builds and a stable/nightly update channel (#1608)

* feat(updater): nightly builds and a stable/nightly update channel

Every master push publishes its artifacts as a prerelease of
4gray/iptvnator-nightly instead of the rolling test-master draft, with a
version of <next patch>-nightly.<commit date>.<run number> applied in
every build job. Settings → About gains an Update channel switch;
AppUpdateService re-points electron-updater per check (feed repository,
allowPrerelease, channel name, allowDowngrade reset) and reads release
notes from the repository the requested version belongs to. Channel
switches are forward-only: a nightly build stays until a newer stable
release exists.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* fix(updater): compute the nightly version once and keep re-runs safe

Review follow-ups: the nightly version is resolved by a leading job and
handed to every build job, and the patch is bumped only when the base
tag already exists so the release-cut window stays below the imminent
release. A re-run never deletes a published nightly; only a draft left
by a failed run is replaced. Typed update-status literals in the
remaining specs carry the new channel fields.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

* test(packaging): expect the nightly-version prerequisite in the build workflow graph

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

apps/web/src/app/services/app-update-install.service.spec.ts

@@ -12,6 +12,9 @@ const BASE_STATUS: ElectronBridgeAppUpdateStatus = {
     currentVersion: '0.23.0',
     status: ELECTRON_BRIDGE_APP_UPDATE_STATUSES.Idle,
     supportedSelfUpdate: true,
+    manualDownloadUrl: 'https://github.com/4gray/iptvnator/releases/latest',
+    channel: 'stable',
+    installedChannel: 'stable',
 };
 
 /**