Solo watching and a clearer offline start

Putting anything up offline starts a solo session: an in-app server bound
to 127.0.0.1 only, joined like hosting, so tracking, next episode and the
player all work. Invite friends re-hosts on the Host card's port and
password with the same media and position; Stop needs no confirmation.
Offline, the Library opens with a welcome band (Join a friend, Host, Watch
solo); without a Jellyfin account it leads with Files and Link, Jellyfin
is an optional card. Play buttons work offline.

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

apps/desktop/lib/src/shell/profile_card.dart

@@ -78,7 +78,7 @@ class _ProfileCardState extends State<ProfileCard> {
           final coord = session.coordinator;
           final online = session.route.value == AppRoute.session;
           final self = online ? coord.selfMember.value : null;
-          final hosting = online && coord.hostFile != null;
+          final hosting = online && !session.solo.value && coord.hostFile != null;
           final color = _p.color.value;
           final png = _p.picture.value;
           final out = self?.out ?? false;