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/settings/settings.component.ts

@@ -42,6 +42,7 @@ import {
     SETTINGS_EPG_VIEW_MODE_OPTIONS,
     SETTINGS_STARTUP_BEHAVIOR_OPTIONS,
     SETTINGS_STARTUP_WINDOW_MODE_OPTIONS,
+    SETTINGS_UPDATE_CHANNEL_OPTIONS,
     SETTINGS_THEME_OPTIONS,
 } from './settings-options';
 import { SettingsPlaybackSectionComponent } from './settings-playback-section.component';
@@ -169,6 +170,7 @@ export class SettingsComponent
     readonly coverSizeOptions = SETTINGS_COVER_SIZE_OPTIONS;
     readonly startupBehaviorOptions = SETTINGS_STARTUP_BEHAVIOR_OPTIONS;
     readonly startupWindowModeOptions = SETTINGS_STARTUP_WINDOW_MODE_OPTIONS;
+    readonly updateChannelOptions = SETTINGS_UPDATE_CHANNEL_OPTIONS;
     readonly epgViewModeOptions = SETTINGS_EPG_VIEW_MODE_OPTIONS;
 
     readonly sectionNavItems: SettingsSection[] = buildSettingsSectionNavItems({