feat(studio): show module origin store ('from <store>')

StoreItem gains source (mapped from StoreEntry.source); the store grid
shows a 'from <store>' label for operator-added stores (bundled seed
unlabelled). Foundation for grouping by store. EN+DE l10n.

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/data/hub.dart

@@ -786,6 +786,7 @@ class HubService {
             kind: e.kind,
             provider: e.provider,
             sourceKind: e.sourceKind,
+            source: e.source,
           ),
         )
         .toList();
@@ -1793,6 +1794,12 @@ class StoreItem {
   /// from `kind` for pre-0.12 hubs.
   final String sourceKind;
 
+  /// Name of the store this entry came from ("bundled" for the built-in
+  /// seed, otherwise the operator-added store's name). Distinct from
+  /// `sourceKind` (the transport) — this is the ORIGIN store, used to
+  /// label and group modules by where they came from.
+  final String source;
+
   bool get isFederated => kind == 'federated';
 
   const StoreItem({
@@ -1817,5 +1824,6 @@ class StoreItem {
     required this.kind,
     required this.provider,
     this.sourceKind = '',
+    this.source = '',
   });
 }