feat(web): 配置历史对比改为左右分栏，支持修改行识别

- 对比视图从上下布局改为左右分栏（当前生效 vs 历史版本）
- 新增 modified 行类型，相邻的删除+新增行配对标记为已修改（黄色高亮）
- 移除 diff npm 依赖，改用内置 LCS 算法实现行级对比
- 弹窗宽度调整为 1200px 适配双栏布局

web/package.json

@@ -9,14 +9,14 @@
     "preview": "vite preview"
   },
   "dependencies": {
+    "axios": "^1.6.0",
+    "element-ui": "^2.15.14",
     "vue": "^2.7.16",
     "vue-router": "^3.6.5",
-    "vuex": "^3.6.2",
-    "element-ui": "^2.15.14",
-    "axios": "^1.6.0"
+    "vuex": "^3.6.2"
   },
   "devDependencies": {
-    "vite": "^5.0.0",
-    "@vitejs/plugin-vue2": "^2.3.1"
+    "@vitejs/plugin-vue2": "^2.3.1",
+    "vite": "^5.0.0"
   }
 }