Show crests and league sections when picking a club

The club chooser was a flat list of 56 names in a generic picker
dialog, which is unreadable from a couch. It now has its own dialog
with a crest per row, the short label on the right, and section
headers per division. Enabled clubs in the settings card show their
crest too.

A search field would have been the obvious alternative, but text
entry on a remote is exactly what the Ten-Foot rule rules out, so
grouping plus crests carries the recognition instead.

Also adds tests/demo, a generator for neutral playlist and EPG data
so screenshots never carry real channel names.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitignore

@@ -6,3 +6,5 @@ local.properties
 .kotlin/
 tests/runs/
 app/src/main/assets/crests/
+tests/demo/playlist.m3u
+tests/demo/epg.xml