Share says why an episode gets no play link (#454)

A private feed's episode, or one ipx-play could not make a link for,
was offered its own address with no word of why, so someone expecting
a page anyone can play could not tell it was on purpose. The menu now
says the feed is private to them, or that the link could not be made
just now, beside the warning for an address carrying their access.

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

tests/ui/app.spec.ts

@@ -2266,6 +2266,7 @@ test('Share hands the feed, and an episode as a link to its page on ipx-play (#4
     const e = (await api('/api/feeds/paid-show/entries') as ListPage).entries[0];
     await shareEpisode({ ...e, link: 'https://www.patreon.com/posts/1?auth=secret123' }, null);
   });
+  await expect(page.locator('#modalCard')).toContainText('private to you');
   await expect(page.locator('#modalCard')).toContainText('includes your own access');
   await expect(page.locator('#shat')).toHaveCount(0);
   await page.locator('#shlink').click();