test(e2e): find a finished programme for the phone dialog after UTC midnight

The Xtream mock lays its 30-minute EPG slots out relative to now, and the
list view shows the programmes that overlap the selected day. In the
first half hour after midnight (the spec pins TZ=UTC) today holds only
the programme on air, so 'stacks the programme dialog actions on a phone'
found no data-when=past row and failed every retry on #1929's Windows
shard (00:18-00:23 UTC). The spec now waits for the list, and steps back
a day when today has no finished programme yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/electron-backend-e2e/src/epg-timeline-interaction.e2e.ts

@@ -331,6 +331,7 @@ test('@epg @xtream @electron stacks the programme dialog actions on a phone', as
     ) as {
         WORKSPACE: { SHELL: { RAIL_LIVE: string } };
         EPG: {
+            PREVIOUS_DAY: string;
             PROGRAM_DIALOG: { SHOW_PROGRAM_DETAILS: string };
             TIMELINE: { WATCH_FROM_START: string };
         };
@@ -365,6 +366,15 @@ test('@epg @xtream @electron stacks the programme dialog actions on a phone', as
             .first()
             .click();
         const guide = app.mainWindow.locator('app-epg-list-view');
+        await expect(guide.locator('[data-when="now"]').first()).toBeVisible();
+        // The mock's 30-minute slots run relative to now, so in the first half
+        // hour after UTC midnight today holds only the programme on air: step
+        // back a day for a finished one.
+        if ((await guide.locator('[data-when="past"]').count()) === 0) {
+            await guide
+                .getByRole('button', { name: fr.EPG.PREVIOUS_DAY })
+                .click();
+        }
         await expect(guide.locator('[data-when="past"]').first()).toBeVisible();
 
         // The window cannot shrink below its desktop minimum, so emulate a