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/dashboard_admin.dart

@@ -8,6 +8,8 @@ class DashboardUserManagementSubBar extends StatelessWidget {
   final ValueChanged<int> onSubTabChange;
   final TextEditingController searchController;
   final String searchHint;
+  /// Infobulle au survol de la barre de recherche (ex. critères de recherche).
+  final String? searchTooltip;
   final Widget? filterControl;
   final VoidCallback? onAddPressed;
   final String addLabel;
@@ -22,12 +24,16 @@ class DashboardUserManagementSubBar extends StatelessWidget {
     'Administrateurs',
   ];
 
+  /// Aligné sur la taille des libellés d’onglets.
+  static const double _searchFontSize = 13;
+
   const DashboardUserManagementSubBar({
     Key? key,
     required this.selectedSubIndex,
     required this.onSubTabChange,
     required this.searchController,
     required this.searchHint,
+    this.searchTooltip,
     this.filterControl,
     this.onAddPressed,
     this.addLabel = '+ Ajouter',
@@ -54,22 +60,7 @@ class DashboardUserManagementSubBar extends StatelessWidget {
             _buildSubNavItem(context, labels[i], i),
           ],
           const SizedBox(width: 36),
-          _pillField(
-            width: 320,
-            child: TextField(
-              controller: searchController,
-              decoration: InputDecoration(
-                hintText: searchHint,
-                prefixIcon: const Icon(Icons.search, size: 18),
-                border: InputBorder.none,
-                isDense: true,
-                contentPadding: const EdgeInsets.symmetric(
-                  horizontal: 10,
-                  vertical: 8,
-                ),
-              ),
-            ),
-          ),
+          _buildSearchField(),
           if (filterControl != null) ...[
             const SizedBox(width: 12),
             _pillField(width: 150, child: filterControl!),
@@ -81,6 +72,40 @@ class DashboardUserManagementSubBar extends StatelessWidget {
     );
   }
 
+  Widget _buildSearchField() {
+    final field = _pillField(
+      width: 320,
+      child: TextField(
+        controller: searchController,
+        style: const TextStyle(fontSize: _searchFontSize),
+        decoration: InputDecoration(
+          hintText: searchHint,
+          hintStyle: TextStyle(
+            fontSize: _searchFontSize,
+            fontStyle: FontStyle.normal,
+            fontWeight: FontWeight.normal,
+            color: Colors.black45,
+          ),
+          prefixIcon: const Icon(Icons.search, size: 18),
+          border: InputBorder.none,
+          isDense: true,
+          contentPadding: const EdgeInsets.symmetric(
+            horizontal: 10,
+            vertical: 8,
+          ),
+        ),
+      ),
+    );
+    final tip = (searchTooltip ?? '').trim();
+    if (tip.isEmpty) return field;
+    return Tooltip(
+      message: tip,
+      preferBelow: false,
+      waitDuration: const Duration(milliseconds: 400),
+      child: field,
+    );
+  }
+
   Widget _pillField({required double width, required Widget child}) {
     return Container(
       width: width,