fix(#153): peaufiner cartes dossiers et recherche.

Cartes neutres avec accent icône, photo AM si dispo, hint court
et infobulle de critères sur la barre de recherche.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/lib/widgets/admin/common/admin_user_card.dart

@@ -12,6 +12,10 @@ class AdminUserCard extends StatefulWidget {
   final Color? backgroundColor;
   final Color? titleColor;
   final Color? infoColor;
+  /// Fond du cercle avatar / icône (défaut lavande admin).
+  final Color? avatarBackgroundColor;
+  /// Couleur de l’icône fallback (défaut violet admin).
+  final Color? avatarIconColor;
   final String? vigilanceTooltip;
   final VoidCallback? onCardTap;
   final EdgeInsetsGeometry? margin;
@@ -28,6 +32,8 @@ class AdminUserCard extends StatefulWidget {
     this.backgroundColor,
     this.titleColor,
     this.infoColor,
+    this.avatarBackgroundColor,
+    this.avatarIconColor,
     this.vigilanceTooltip,
     this.onCardTap,
     this.margin,
@@ -159,8 +165,8 @@ class _AdminUserCardState extends State<AdminUserCard> {
 
   Widget _buildAvatar(String url) {
     const size = 28.0;
-    const bg = Color(0xFFEDE5FA);
-    const iconColor = Color(0xFF6B3FA0);
+    final bg = widget.avatarBackgroundColor ?? const Color(0xFFEDE5FA);
+    final iconColor = widget.avatarIconColor ?? const Color(0xFF6B3FA0);
 
     if (url.isEmpty) {
       return CircleAvatar(