Revert the jellyfin-only default introduced by PR #123 so upgrading
users keep their online sources; Jellyfin becomes opt-in:
- default enabledProviders is now the online set (netease/qq/bilibili/
youtube/kugou); defaultPlatform() uses a fixed priority order
(netease -> qq -> kugou -> jellyfin -> bilibili -> youtube) instead
of jellyfin-first, so chat/REST/WebUI default to netease again
- Settings: Jellyfin card is always visible with a new enable toggle
(its enabled bit is enabledProviders membership); guards against
clobbering other providers before the list loads
- Setup wizard: saving the Jellyfin step auto-enables the source when
a server URL was entered
- Search/player store fallbacks flip from jellyfin to netease; !help
no longer hardcodes Jellyfin lines
- tests: update default-platform assertions, add coverage for the new
default set, legacy configs without enabledProviders, priority
order, and explicit jellyfin-only configs
- README: reframe Jellyfin as optional (badges, command table, quality
tiers, dedicated section, changelog), document the enabledProviders
default and the v1.10.0 jellyfin-only window fix, credit @ItsEricRao
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
