feat(ui): la carte reprend l'image importée en fond (voile pour lisibilité)

- ServerCard: fond = image (MemoryImage) + scrim dégradé si présente, sinon
  dégradé thématique ; vignette d'icône masquée quand image de fond.
- servers_screen: fetch des bytes image (cache par id, vidé au refresh) → passe
  à la carte ; plus de FutureBuilder iconUrl inutile.

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

lib/widgets/server_card.dart

@@ -1,3 +1,5 @@
+import 'dart:typed_data';
+
 import 'package:flutter/material.dart';
 import 'package:url_launcher/url_launcher.dart';
 
@@ -11,6 +13,7 @@ class ServerCard extends StatelessWidget {
     required this.busy,
     required this.onToggle,
     this.onTap,
+    this.imageBytes,
   });
 
   final GameServer server;
@@ -18,31 +21,49 @@ class ServerCard extends StatelessWidget {
   final bool busy;
   final VoidCallback onToggle;
   final VoidCallback? onTap;
+  final Uint8List? imageBytes;
 
   @override
   Widget build(BuildContext context) {
     final t = server.theme;
     final badge = server.statusBadge;
+    final hasImg = imageBytes != null;
     return Card(
       clipBehavior: Clip.antiAlias,
       child: InkWell(
         onTap: onTap,
+        child: Ink(
+        decoration: hasImg
+            ? BoxDecoration(
+                image: DecorationImage(image: MemoryImage(imageBytes!), fit: BoxFit.cover),
+              )
+            : BoxDecoration(
+                gradient: LinearGradient(
+                  begin: Alignment.topLeft,
+                  end: Alignment.bottomRight,
+                  colors: [t.start, t.end],
+                ),
+              ),
         child: Container(
-        decoration: BoxDecoration(
-          gradient: LinearGradient(
-            begin: Alignment.topLeft,
-            end: Alignment.bottomRight,
-            colors: [t.start, t.end],
-          ),
-        ),
+        decoration: hasImg
+            ? const BoxDecoration(
+                gradient: LinearGradient(
+                  begin: Alignment.topCenter,
+                  end: Alignment.bottomCenter,
+                  colors: [Color(0x66000000), Color(0xCC000000)],
+                ),
+              )
+            : null,
         padding: const EdgeInsets.all(18),
         child: Column(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [
             Row(
               children: [
-                _Icon(server: server, iconUrl: iconUrl, fallback: t.icon),
-                const SizedBox(width: 14),
+                if (!hasImg) ...[
+                  _Icon(server: server, iconUrl: iconUrl, fallback: t.icon),
+                  const SizedBox(width: 14),
+                ],
                 Expanded(
                   child: Column(
                     crossAxisAlignment: CrossAxisAlignment.start,
@@ -107,6 +128,7 @@ class ServerCard extends StatelessWidget {
         ),
       ),
       ),
+      ),
     );
   }
 }
@@ -124,7 +146,7 @@ class _Icon extends StatelessWidget {
       child: SizedBox(
         width: 52,
         height: 52,
-        child: (server.hasIcon)
+        child: (server.hasIcon && iconUrl.isNotEmpty)
             ? Image.network(iconUrl,
                 fit: BoxFit.cover,
                 errorBuilder: (_, __, ___) => _fallbackBox())