refactor: 重构纹理图集工具，实现浏览器端实时处理

将合图处理从服务端迁移到浏览器端，使用 Web Worker 实现高性能打包算法，新增三栏布局界面和精灵动画预览功能

- 新增 atlasStore 状态管理，实现文件、配置、结果的统一管理
- 新增 atlas-packer 打包算法库（MaxRects/Shelf），支持浏览器端快速合图
- 新增 atlas-worker Web Worker，实现异步打包处理避免阻塞 UI
- 新增三栏布局组件：FileListPanel、CanvasPreview、AtlasConfigPanel
- 新增 AnimationPreviewDialog 支持精灵动画帧预览和帧率控制
- 优化所有工具页面的响应式布局和交互体验

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/locales/en.json

@@ -333,6 +333,30 @@
     "dragHint": "Drag slider or click to compare",
     "filename": "Filename"
   },
+  "atlas": {
+    "dropSprites": "Drop sprites here",
+    "supportFolder": "Supports folder drag and drop",
+    "selectFiles": "Select Files",
+    "selectFolder": "Select Folder",
+    "preview": "Preview",
+    "emptyPreview": "Upload sprites to preview atlas",
+    "dragHint": "Drag files or folder to left panel",
+    "panHint": "Drag to pan, scroll to zoom",
+    "packing": "Packing...",
+    "rendering": "Rendering...",
+    "previewAnimation": "Preview Animation",
+    "sizeSettings": "Size Settings",
+    "layoutSettings": "Layout Settings",
+    "outputSettings": "Output Settings",
+    "resultInfo": "Atlas Info",
+    "animationPreview": "Animation Preview",
+    "animationDescription": "Preview sprite sequence animation",
+    "frame": "Frame",
+    "fps": "FPS",
+    "spriteSize": "Sprite Size",
+    "totalFrames": "Total Frames",
+    "duration": "Duration"
+  },
   "footer": {
     "tagline": "Media processing tools for game developers. Extract frames, compress images, optimize audio.",
     "note": "Inspired by modern product storytelling—centered on your workflow, not UI noise.",