refactor: 将 WebUI 源码纳入仓库,移除打包产物

- 新增 webui/ 前端源码目录（React+Vite+TypeScript+Tailwind）
- 删除 api/webui/ 中旧的打包静态资源
- 更新 .gitignore 忽略 api/webui/ 构建输出和 webui/node_modules
- 更新 README 增加前端构建说明

webui/src/i18n/locales/en-US/data.json

@@ -0,0 +1,29 @@
+{
+  "dialog": {
+    "button": "PAYLOAD_MATRIX",
+    "title": "DATA_EXPLORER"
+  },
+  "explorer": {
+    "title": "CAPTURED_PAYLOAD_MATRIX",
+    "records": "{{count}} RECORDS",
+    "rescan": "RESCAN",
+    "loading": "[LOADING] Scanning payload directory...",
+    "noData": "NO_DATA_CAPTURED",
+    "noDataHint": "Initialize crawler to begin data extraction sequence. Results will appear here upon completion.",
+    "allCategories": "ALL"
+  },
+  "file": {
+    "entries": "{{count}} entries",
+    "extract": "EXTRACT",
+    "preview": "PREVIEW"
+  },
+  "preview": {
+    "title": "Data Preview",
+    "records": "{{count}} RECORDS",
+    "download": "DOWNLOAD",
+    "loading": "[LOADING] Decoding payload...",
+    "error": "[ERROR] Failed to decode payload",
+    "searchPlaceholder": "Search in data...",
+    "showing": "Showing {{filtered}} of {{total}} records"
+  }
+}