重新设计diff功能：使用Monaco Editor实现专业级文件对比

新增功能：
- DiffViewer组件：基于Monaco Editor DiffEditor的专业代码对比
- DiffWindow组件：专用的diff对比窗口包装器
- 并排/内联视图切换功能
- 多语言语法高亮支持
- 智能文件类型检测
- 完整的工具栏（下载、刷新、视图切换、行号切换）

技术改进：
- 替代原来的两个独立文件窗口方案
- 使用Monaco Editor提供VS Code同级的对比体验
- 支持大文件错误处理和SSH连接自动重连
- 专业的差异高亮显示（新增/删除/修改）

依赖更新：
- 新增@monaco-editor/react依赖

package-lock.json

@@ -9,6 +9,7 @@
       "version": "1.6.0",
       "dependencies": {
         "@hookform/resolvers": "^5.1.1",
+        "@monaco-editor/react": "^4.7.0",
         "@radix-ui/react-accordion": "^1.2.11",
         "@radix-ui/react-avatar": "^1.1.10",
         "@radix-ui/react-checkbox": "^1.3.2",
@@ -2950,6 +2951,29 @@
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       "license": "MIT"
     },
+    "node_modules/@monaco-editor/loader": {
+      "version": "1.5.0",
+      "resolved": "https://registry.npmjs.org/@monaco-editor/loader/-/loader-1.5.0.tgz",
+      "integrity": "sha512-hKoGSM+7aAc7eRTRjpqAZucPmoNOC4UUbknb/VNoTkEIkCPhqV8LfbsgM1webRM7S/z21eHEx9Fkwx8Z/C/+Xw==",
+      "license": "MIT",
+      "dependencies": {
+        "state-local": "^1.0.6"
+      }
+    },
+    "node_modules/@monaco-editor/react": {
+      "version": "4.7.0",
+      "resolved": "https://registry.npmjs.org/@monaco-editor/react/-/react-4.7.0.tgz",
+      "integrity": "sha512-cyzXQCtO47ydzxpQtCGSQGOC8Gk3ZUeBXFAxD+CWXYFo5OqZyZUonFl0DwUlTyAfRHntBfw2p3w4s9R6oe1eCA==",
+      "license": "MIT",
+      "dependencies": {
+        "@monaco-editor/loader": "^1.5.0"
+      },
+      "peerDependencies": {
+        "monaco-editor": ">= 0.25.0 < 1",
+        "react": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0",
+        "react-dom": "^16.8.0 || ^17.0.0 || ^18.0.0 || ^19.0.0"
+      }
+    },
     "node_modules/@nodelib/fs.scandir": {
       "version": "2.1.5",
       "resolved": "https://registry.npmjs.org/@nodelib/fs.scandir/-/fs.scandir-2.1.5.tgz",
@@ -5311,6 +5335,13 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@types/trusted-types": {
+      "version": "1.0.6",
+      "resolved": "https://registry.npmjs.org/@types/trusted-types/-/trusted-types-1.0.6.tgz",
+      "integrity": "sha512-230RC8sFeHoT6sSUlRO6a8cAnclO06eeiq1QDfiv2FGCLWFvvERWgwIQD4FWqD9A69BN7Lzee4OXwoMVnnsWDw==",
+      "license": "MIT",
+      "peer": true
+    },
     "node_modules/@types/verror": {
       "version": "1.10.11",
       "resolved": "https://registry.npmjs.org/@types/verror/-/verror-1.10.11.tgz",
@@ -12234,6 +12265,16 @@
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       "license": "MIT"
     },
+    "node_modules/monaco-editor": {
+      "version": "0.53.0",
+      "resolved": "https://registry.npmjs.org/monaco-editor/-/monaco-editor-0.53.0.tgz",
+      "integrity": "sha512-0WNThgC6CMWNXXBxTbaYYcunj08iB5rnx4/G56UOPeL9UVIUGGHA1GR0EWIh9Ebabj7NpCRawQ5b0hfN1jQmYQ==",
+      "license": "MIT",
+      "peer": true,
+      "dependencies": {
+        "@types/trusted-types": "^1.0.6"
+      }
+    },
     "node_modules/mri": {
       "version": "1.1.4",
       "resolved": "https://registry.npmjs.org/mri/-/mri-1.1.4.tgz",
@@ -14891,6 +14932,12 @@
         "node": ">= 6"
       }
     },
+    "node_modules/state-local": {
+      "version": "1.0.7",
+      "resolved": "https://registry.npmjs.org/state-local/-/state-local-1.0.7.tgz",
+      "integrity": "sha512-HTEHMNieakEnoe33shBYcZ7NX83ACUjCu8c40iOGEZsngj9zRnkqS9j1pqQPXwobB0ZcVTk27REb7COQ0UR59w==",
+      "license": "MIT"
+    },
     "node_modules/statuses": {
       "version": "2.0.2",
       "resolved": "https://registry.npmjs.org/statuses/-/statuses-2.0.2.tgz",