fix: improve mobile layout on meals page and navigation

- Dashboard: stack days vertically on mobile and suppress empty meal slots
- Nav: allow wrapping on narrow screens
- MealDetail: responsive hero sizing and padding

frontend/src/pages/MealDetail.tsx

@@ -170,34 +170,34 @@ export default function MealDetail() {
           <img
             src={recipe.image_url}
             alt={recipe.name}
-            className="w-full h-72 object-cover opacity-90"
+            className="w-full h-48 sm:h-72 object-cover opacity-90"
           />
         ) : (
-          <div className="h-72 flex items-center justify-center">
+          <div className="h-48 sm:h-72 flex items-center justify-center">
             <ChefHat className="w-16 h-16 text-surface-600" />
           </div>
         )}
         <div className="absolute inset-0 bg-gradient-to-t from-black/70 via-black/20 to-transparent" />
-        <div className="absolute bottom-0 left-0 right-0 p-6">
-          <div className="flex items-end justify-between gap-4">
+        <div className="absolute bottom-0 left-0 right-0 p-4 sm:p-6">
+          <div className="flex flex-col sm:flex-row sm:items-end sm:justify-between gap-3">
             <div>
-              <h1 className="text-3xl font-bold text-white">{recipe.name}</h1>
+                <h1 className="text-xl sm:text-3xl font-bold text-white">{recipe.name}</h1>
               {recipe.description && (
-                <p className="text-white/80 mt-1 max-w-xl text-sm">{recipe.description}</p>
+                <p className="text-white/80 mt-1 max-w-xl text-xs sm:text-sm">{recipe.description}</p>
               )}
             </div>
-            <div className="text-right flex-shrink-0">
-              <div className="text-2xl font-bold text-white">
+            <div className="text-left sm:text-right flex-shrink-0">
+              <div className="text-xl sm:text-2xl font-bold text-white">
                 ${item.estimated_cost?.toFixed(2) || 'N/A'}
               </div>
-              <div className="text-sm text-white/70">per serving</div>
+              <div className="text-xs sm:text-sm text-white/70">per serving</div>
             </div>
           </div>
         </div>
       </div>
 
       {/* Metadata Row */}
-      <div className="flex flex-wrap items-center gap-4">
+      <div className="flex flex-wrap items-center gap-3">
         {totalTime > 0 && (
           <div className="flex items-center gap-1.5 text-sm text-surface-600 bg-surface-100 px-3 py-1.5 rounded-lg">
             <Clock className="w-4 h-4 text-surface-500" />