fix: 修复行程卡片间距被 last:mb-0 清零的问题

每个 SortablePlanItem 被 motion.div 包裹，last:mb-0 会对
所有 item 生效导致 mb-5 失效，移除 last:mb-0 即可。
同步优化卡片内部间距、padding、reason 加分隔线。

src/components/BlindboxPlan.tsx

@@ -197,13 +197,13 @@ function SortablePlanItem({ id, item, canEdit, onEdit }: SortablePlanItemProps)
   };
 
   return (
-    <div ref={setNodeRef} style={style} className="relative mb-4 last:mb-0">
+    <div ref={setNodeRef} style={style} className="relative mb-5">
-      <div className="absolute -left-6 top-3 flex h-[18px] w-[18px] items-center justify-center rounded-full bg-purple-600/20 ring-2 ring-background">
+      <div className="absolute -left-6 top-4 flex h-[18px] w-[18px] items-center justify-center rounded-full bg-purple-600/20 ring-2 ring-background">
         <div className="h-2 w-2 rounded-full bg-purple-400" />
       </div>
 
-      <div className="rounded-xl bg-surface/80 p-3.5 ring-1 ring-border/80">
+      <div className="rounded-2xl bg-surface/80 p-4 ring-1 ring-border/80">
-        <div className="flex items-start gap-2">
+        <div className="flex items-start gap-2.5">
           {canEdit && (
             <button
               {...attributes}
@@ -214,20 +214,20 @@ function SortablePlanItem({ id, item, canEdit, onEdit }: SortablePlanItemProps)
               <GripVertical size={14} />
             </button>
           )}
-          <span className="mt-0.5 text-sm font-black text-purple-400">{item.time}</span>
+          <span className="mt-0.5 min-w-[38px] text-sm font-black text-purple-400">{item.time}</span>
           <div className="min-w-0 flex-1">
             <div className="flex items-center gap-1.5">
               <CategoryBadge category={guessCategory(item.activity)} />
               <p className="truncate text-sm font-bold text-heading">{item.activity}</p>
             </div>
-            <div className="mt-1.5 flex items-center gap-1 text-[11px] text-muted">
+            <div className="mt-2 flex items-center gap-1 text-[11px] text-muted">
               <MapPin size={10} className="shrink-0" />
               <span className="truncate">{item.poi}</span>
             </div>
             {item.address && (
-              <p className="mt-0.5 truncate text-[10px] text-dim">{item.address}</p>
+              <p className="mt-1 truncate text-[10px] text-dim">{item.address}</p>
             )}
-            <div className="mt-2 flex items-center gap-3">
+            <div className="mt-2.5 flex items-center gap-3">
               <span className="flex items-center gap-1 text-[10px] text-dim">
                 <Clock size={9} />
                 {formatDuration(item.duration)}
@@ -245,7 +245,7 @@ function SortablePlanItem({ id, item, canEdit, onEdit }: SortablePlanItemProps)
               )}
             </div>
             {item.reason && (
-              <p className="mt-1.5 text-[10px] leading-relaxed text-dim italic">
+              <p className="mt-2.5 border-t border-border/30 pt-2 text-[10px] leading-relaxed text-dim italic">
                 {item.reason}
               </p>
             )}
@@ -434,13 +434,13 @@ export default function BlindboxPlan({
         <AnimatePresence mode="wait">
           <motion.div
             key={dayIndex}
-            className="relative mx-auto max-w-sm pl-6"
+            className="relative mx-auto max-w-sm px-4 pb-2 pl-9"
             initial={{ opacity: 0, x: 20 }}
             animate={{ opacity: 1, x: 0 }}
             exit={{ opacity: 0, x: -20 }}
             transition={{ duration: 0.25 }}
           >
-            <div className="absolute left-[9px] top-2 bottom-2 w-px bg-purple-500/20" />
+            <div className="absolute left-[21px] top-2 bottom-2 w-px bg-purple-500/20" />
 
             <DndContext
               key={dayIndex}