feat(explore): your own studyset is yours, not one to add

Explore offered Add on the author's own published studyset and made a
whole second copy of it beside the original. The instance now names
the studyset an entry was published from to its author alone
(`yourStudysetId`, never to anyone else), and Explore shows it as Yours,
opening the original, while it is in the library. The summary still
adds a copy anyway, to see it as learners get it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_localizations_en.dart

@@ -6276,6 +6276,12 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get exploreInLibrary => 'In your library';
 
+  @override
+  String get exploreYours => 'Yours';
+
+  @override
+  String get exploreAddCopyAnyway => 'Add a copy anyway';
+
   @override
   String explorePercent(int percent) {
     return '$percent %';