revert(diy): 撤销贴纸坐标钳制，恢复可拖出画布外自由摆放

需求决定（2026-09-12）：负坐标/超出画布为合法摆放状态；
重叠误报根因是尺寸语义（已由归一化修复），坐标钳制一并移除。
文档同步标注该决策。

Co-Authored-By: Claude <noreply@anthropic.com>

src/pages/diy/index.tsx

@@ -297,16 +297,10 @@ export default function DIYPage() {
   const handleStickerTouchMove = (e: any) => {
     if (!isDragging || !activeStickerId) return
     const touch = e.touches[0]
+    // 需求决定（2026-09-12）：贴纸允许拖出画布外自由摆放，不做坐标钳制
     const next = stickers.map(s => {
       if (s.id !== activeStickerId) return s
-      // 问题1 修正：坐标钳制在画布内，杜绝负坐标与拖出画布（碰撞盒 = x/y + 显示宽高）
-      const maxX = Math.max(0, category.mask.width - s.width * s.scale)
-      const maxY = Math.max(0, category.mask.height - s.height * s.scale)
-      return {
-        ...s,
-        x: Math.min(Math.max(touch.clientX - startPos.x, 0), maxX),
-        y: Math.min(Math.max(touch.clientY - startPos.y, 0), maxY)
-      }
+      return { ...s, x: touch.clientX - startPos.x, y: touch.clientY - startPos.y }
     })
     const checked = checkOverlap(next)
     setStickers(checked)
@@ -325,16 +319,7 @@ export default function DIYPage() {
   const handleScale = (id: string, delta: number) => {
     const next = stickers.map(s => {
       if (s.id !== id) return s
-      const scale = Math.max(0.3, Math.min(3, s.scale + delta))
-      // 问题1 修正：缩放后把位置钳回画布内
-      const maxX = Math.max(0, category.mask.width - s.width * scale)
-      const maxY = Math.max(0, category.mask.height - s.height * scale)
-      return {
-        ...s,
-        scale,
-        x: Math.min(Math.max(s.x, 0), maxX),
-        y: Math.min(Math.max(s.y, 0), maxY)
-      }
+      return { ...s, scale: Math.max(0.3, Math.min(3, s.scale + delta)) }
     })
     const checked = checkOverlap(next)
     setStickers(checked)