feat(s2a): Improve ProfileCard layout with flexbox for consistent height

- Add flex flex-col and h-full to Card component for full height layout
- Update CardContent with flex flex-col flex-1 for proper content distribution
- Move action buttons to bottom with mt-auto pt-4 spacing
- Ensures profile cards maintain consistent heights in grid layout and action buttons align to bottom

frontend/src/pages/S2AConfig.tsx

@@ -603,14 +603,14 @@ function ProfileCard({ profile, isActive, isActivating, groupNameCache, onActiva
     try { parsedGroups = JSON.parse(profile.group_ids || '[]') } catch { /* ignore */ }
 
     return (
-        <Card className={`relative transition-all ${isActive ? 'ring-2 ring-green-500 dark:ring-green-400' : ''}`}>
+        <Card className={`relative transition-all flex flex-col h-full ${isActive ? 'ring-2 ring-green-500 dark:ring-green-400' : ''}`}>
             {/* 活动标记 */}
             {isActive && (
                 <div className="absolute -top-2 -right-2 bg-green-500 text-white text-xs px-2 py-0.5 rounded-full font-medium shadow-sm">
                     使用中
                 </div>
             )}
-            <CardContent>
+            <CardContent className="flex flex-col flex-1">
                 {/* 名称 + 操作 */}
                 <div className="flex items-start justify-between mb-3">
                     <div className="flex-1 min-w-0">
@@ -647,7 +647,7 @@ function ProfileCard({ profile, isActive, isActivating, groupNameCache, onActiva
                 )}
 
                 {/* 操作按钮 */}
-                <div className="flex items-center gap-2">
+                <div className="flex items-center gap-2 mt-auto pt-4">
                     {!isActive ? (
                         <Button
                             onClick={onActivate}