fix(servers): stop rebinds from flashing an empty home screen after sign-in

Signing in triggered two back-to-back profile rebinds; the second re-added
the same Jellyfin connection, which tore down the live client and aborted
the home screen's in-flight fetches. The aborted pass was committed as
loaded-empty, flashing 'no content available' until the follow-up load
landed. Fix at the root instead of patching the sign-in window:

- addJellyfinConnection now reuses the live client when the connection is
  unchanged (token, deviceId, URL set), matching the existing Plex
  refreshTokensForProfile behavior; material changes still recreate it.
- Cancelled requests are classified end-to-end: the client's
  treat-as-empty helpers rethrow cancellations, and the aggregation
  fan-outs report cancelledServerIds alongside succeededServerIds.
- A fetch pass in which zero servers succeeded is never authoritative:
  it keeps existing content instead of wiping it (also fixes the
  pre-existing blanking of home/sidebar on a totally failed refresh),
  stays in loading while disrupted (cancellation or binding in flight),
  and only commits loaded-empty on a settled failure.

lib/navigation/profile_session_screen.dart

@@ -144,10 +144,14 @@ class _ProfileSessionScreenState extends State<ProfileSessionScreen> {
                 lazy: true,
               ),
               ChangeNotifierProvider(
-                create: (context) => LibrariesProvider(
-                  storageService: context.read<StorageService>(),
-                  multiServer: context.read<MultiServerProvider>(),
-                ),
+                create: (context) {
+                  final activeProfile = context.read<ActiveProfileProvider>();
+                  return LibrariesProvider(
+                    storageService: context.read<StorageService>(),
+                    multiServer: context.read<MultiServerProvider>(),
+                    isProfileBinding: () => activeProfile.isBinding,
+                  );
+                },
               ),
               ChangeNotifierProvider(
                 create: (context) {