feat(studio): store-side source filter, provenance pills, one-click recommended sources (v0.29.0)

The Store is now the centre of capability discovery — provider
configuration moves out of Settings into the Store itself.
Three changes work together:

1. Source filter chips next to the existing status chips:
   All sources / Native / MCP / n8n. Applied client-side after
   the hub returns results so toggling is instant. The result
   count and the "Clear filters" reset both account for the
   source filter too.

2. Per-card provenance pill (`_ProvenancePill`): shows whether
   each entry is native, mcp · <provider>, or n8n · <provider>
   so the operator can triage the source at a glance — same
   role the "verified" badge plays in commercial app stores.

3. `_RecommendedSourcesStrip` replaces the older
   `_FederationNudge`. Renders curated public MCP servers
   (DeepWiki, Semgrep) as one-click cards with an inline
   `[+ Add]` button — no Settings detour, no form. Both servers
   are HTTPS Streamable-HTTP, no API key, no subprocess.
   Useful AI was considered but its 340+ tools would drown the
   index — kept out of the curated list. The strip auto-hides
   the moment any federated entry exists.

Removed the now-orphaned storeFederationNudge* ARB keys.

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

lib/l10n/app_localizations_de.dart

@@ -471,14 +471,70 @@ class AppLocalizationsDe extends AppLocalizations {
   String get storeDocsErrorGeneric => 'README konnte nicht geladen werden.';
 
   @override
-  String get storeFederationNudgeTitle => 'Mehr Capabilities?';
+  String get storeSourceLabel => 'Quelle';
 
   @override
-  String get storeFederationNudgeBody =>
-      'MCP-Server oder n8n-Endpunkt unter Einstellungen → MCP-Clients / N8N-Endpunkte konfigurieren. Entdeckte Tools und Workflows tauchen hier als `mcp.<server>.<tool>`- und `n8n.<endpoint>.<workflow>`-Capabilities auf — jeder Anthropic-/Community-MCP-Server bringt mehrere auf einmal.';
+  String get storeSourceAll => 'Alle Quellen';
 
   @override
-  String get storeFederationNudgeButton => 'Einstellungen öffnen';
+  String get storeSourceNative => 'Nativ';
+
+  @override
+  String get storeSourceMcp => 'MCP';
+
+  @override
+  String get storeSourceN8n => 'n8n';
+
+  @override
+  String get storeProvenanceNative => 'nativ';
+
+  @override
+  String storeProvenanceMcp(String provider) {
+    return 'mcp · $provider';
+  }
+
+  @override
+  String storeProvenanceN8n(String provider) {
+    return 'n8n · $provider';
+  }
+
+  @override
+  String get storeRecommendedTitle =>
+      'Öffentliche Quelle hinzufügen — ein Klick';
+
+  @override
+  String get storeRecommendedBody =>
+      'Kuratierte MCP-Server über HTTPS erreichbar. Kein Subprozess, kein API-Key, kein Node. Föderierte Capabilities erscheinen sofort im Store.';
+
+  @override
+  String get storeRecommendedAddTooltip => 'Hinzufügen und entdecken';
+
+  @override
+  String get storeRecommendedAdding => 'Wird hinzugefügt…';
+
+  @override
+  String get storeRecommendedDeepWikiTagline =>
+      'GitHub-Repo-Doku-Suche (KI-gestützt)';
+
+  @override
+  String get storeRecommendedSemgrepTagline =>
+      'Security-Scanning für Code-Schwachstellen';
+
+  @override
+  String storeProviderAddedToast(String name, int n) {
+    String _temp0 = intl.Intl.pluralLogic(
+      n,
+      locale: localeName,
+      other: 'föderierte Capabilities',
+      one: 'föderierte Capability',
+    );
+    return '$name hinzugefügt — $n $_temp0.';
+  }
+
+  @override
+  String storeProviderAddFailed(String name, String error) {
+    return '$name konnte nicht hinzugefügt werden: $error';
+  }
 
   @override
   String get auditTitle => 'Protokoll';