feat(app,android,ios): a blurred poster where a title has no wide art

A title with no fanart, banner or backdrop drew its poster cropped to the
band's shape across the title page and the library's banner: a blown-up
slice of the middle of it, which read as broken. Now the poster is
squeezed to 64x36 and blurred once when it is fetched, the cache keeps
that wash, and it is stretched across the band. The library's banner
stands the sharp poster at its right over it. Android blurs the poster
it already had (Android 12 and later; older versions decode it tiny),
and iOS likewise.

METADATA.md also records the quality badges of the commit before.

docs/USER_GUIDE.md

@@ -76,6 +76,8 @@ Click a title to open its page. **Esc** goes back.
 - With posters and descriptions on, a show's logo takes the place of its name at the top of the
   page and on the library's banner, and each episode says how long it runs. A film says how long
   it runs in the line under its name.
+- A title with no wide picture shows its poster blurred across the top of the page instead, and
+  on the library's banner the poster itself beside it.
 - The line under the name also says what most of the files are, when their names say it: **4K**,
   **1080p**, **HDR**, **10-bit** or **Dual audio**.