An album whose folder cannot be made no longer stops the backup (closes #197)

Each album's folder, links and JSON are written inside one try. A failure
prints `FAILED album <name>: <reason>`, lists the album's ID in the new
`failedAlbums` of the result and of `--json`, and makes `quak backup` exit 1;
the other albums and `failures.json` are still written.

An album whose folder would have another album's JSON name, ignoring case,
gets its ID. A name over 255 bytes (250 for a folder, which leaves room for
`.json`) gets the ID and is cut short between two characters by
`shortenToBytes` in `src/filename.ts`. A link's ID goes right before its
extension.

Apart from its call to `uniqueNames`, the album loop is only indented into
the try.

Model: opus-5-5

src/cli-commands.ts

@@ -470,7 +470,9 @@ export const backupCommand = async (
                 }
             }
 
-            return result.failed > 0 || result.undecryptableAlbums.length > 0
+            return result.failed > 0 ||
+                result.undecryptableAlbums.length > 0 ||
+                result.failedAlbums.length > 0
                 ? 1
                 : 0;
         } finally {