fix(ui): remove opacity on dropdown items and assign unique bandeau colors by index

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

frontend/lib/widgets/quotidien/couple_selector_bandeau.dart

@@ -64,6 +64,7 @@ class CoupleSelectorBandeau extends StatelessWidget {
         mode: mode,
         couple: selected,
         showChevron: multi,
+        colorIndex: couples.indexOf(selected),
       );
 
       if (!multi) return card;
@@ -102,6 +103,7 @@ class CoupleSelectorBandeau extends StatelessWidget {
                       showChevron: false,
                       selected: false,
                       isMenuItem: true,
+                      colorIndex: couples.indexOf(c),
                     ),
                   ),
                 ),
@@ -120,6 +122,7 @@ class _CoupleCard extends StatelessWidget {
   final bool showChevron;
   final bool selected;
   final bool isMenuItem;
+  final int colorIndex;
 
   const _CoupleCard({
     required this.mode,
@@ -127,44 +130,36 @@ class _CoupleCard extends StatelessWidget {
     required this.showChevron,
     this.selected = true,
     this.isMenuItem = false,
+    required this.colorIndex,
   });
 
   @override
   Widget build(BuildContext context) {
-    // Dans le menu, les non-sélectionnés sont un peu translucides
-    final opacity = (!selected && isMenuItem) ? 0.65 : 1.0;
-
     return Container(
       height: 90,
       decoration: BoxDecoration(
         image: DecorationImage(
-          image: AssetImage(QuotidienTheme.bandeauAssetForCouple(couple.id)), 
+          image: AssetImage(QuotidienTheme.bandeauColors[colorIndex % QuotidienTheme.bandeauColors.length]), 
           fit: BoxFit.fill,
-          opacity: opacity,
         ),
       ),
       padding: const EdgeInsets.symmetric(horizontal: 24),
       child: Row(
         children: [
           Expanded(
-            child: Opacity(
-              opacity: opacity,
             child: _MembreTile(
               photoUrl: couple.enfant.photoUrl,
               name: couple.enfant.displayName(fallback: 'Enfant'),
               fallbackIcon: Icons.child_care,
             ),
           ),
-          ),
           Container(
             width: 1,
             height: 44,
             margin: const EdgeInsets.symmetric(horizontal: 12),
-            color: QuotidienTheme.ink.withValues(alpha: 0.15 * opacity),
+            color: QuotidienTheme.ink.withValues(alpha: 0.15),
           ),
           Expanded(
-            child: Opacity(
-              opacity: opacity,
             child: _MembreTile(
               photoUrl: couple.am.photoUrl,
               name: couple.am.displayName(
@@ -177,13 +172,12 @@ class _CoupleCard extends StatelessWidget {
                   : Icons.person_outline,
             ),
           ),
-          ),
           if (showChevron)
-            Padding(
-              padding: const EdgeInsets.only(left: 4),
+            const Padding(
+              padding: EdgeInsets.only(left: 4),
               child: Icon(
                 Icons.keyboard_arrow_down,
-                color: QuotidienTheme.ink.withValues(alpha: opacity),
+                color: QuotidienTheme.ink,
               ),
             ),
         ],