feat: écran détail serveur (stats CPU/RAM + image importable RustFS)

- carte cliquable → ServerDetailScreen : bannière (image ou thème), statut,
  connexion/ouvrir, joueurs/MOTD, jauges CPU/RAM/réseau (docker stats),
  import/suppression d'image (galerie → backend → RustFS).
- api_service: stats(), server(), imageBytes(), uploadImage(), deleteImage().
- deps: image_picker.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/widgets/server_card.dart

@@ -10,19 +10,24 @@ class ServerCard extends StatelessWidget {
     required this.iconUrl,
     required this.busy,
     required this.onToggle,
+    this.onTap,
   });
 
   final GameServer server;
   final String iconUrl;
   final bool busy;
   final VoidCallback onToggle;
+  final VoidCallback? onTap;
 
   @override
   Widget build(BuildContext context) {
     final t = server.theme;
     final badge = server.statusBadge;
     return Card(
-      child: Container(
+      clipBehavior: Clip.antiAlias,
+      child: InkWell(
+        onTap: onTap,
+        child: Container(
         decoration: BoxDecoration(
           gradient: LinearGradient(
             begin: Alignment.topLeft,
@@ -101,6 +106,7 @@ class ServerCard extends StatelessWidget {
           ],
         ),
       ),
+      ),
     );
   }
 }