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>

tools/packaging/configure-linux-frame-copy-build.test.mjs

@@ -440,7 +440,9 @@ test('keeps non-Linux builds independent from the Linux runtime prerequisite', (
 
     assert.ok(crossPlatformJob);
     assert.ok(linuxJob);
-    assert.equal(crossPlatformJob.needs, undefined);
+    // The nightly-version job is a cheap, platform-neutral prerequisite; the
+    // Linux runtime build must stay out of the non-Linux dependency list.
+    assert.deepEqual(crossPlatformJob.needs, 'nightly-version');
     assert.deepEqual(
         crossPlatformJob.strategy.matrix.include.map(({ os, arch }) => ({
             os,
@@ -453,7 +455,10 @@ test('keeps non-Linux builds independent from the Linux runtime prerequisite', (
         ]
     );
     assert.equal(crossPlatformJob.strategy['fail-fast'], false);
-    assert.equal(linuxJob.needs, 'linux-embedded-mpv-runtime');
+    assert.deepEqual(linuxJob.needs, [
+        'linux-embedded-mpv-runtime',
+        'nightly-version',
+    ]);
     assert.deepEqual(
         linuxJob.strategy.matrix.include.map(
             ({ os, arch, linux_profile: profile }) => ({
@@ -475,6 +480,7 @@ test('keeps non-Linux builds independent from the Linux runtime prerequisite', (
     assert.equal(linuxJob.strategy['fail-fast'], false);
     assert.deepEqual(linuxJob.steps, crossPlatformJob.steps);
     assert.deepEqual(buildWorkflowConfig.jobs['create-release'].needs, [
+        'nightly-version',
         'build-cross-platform',
         'build-linux',
     ]);