feat: 添加完整的前端管理系统 (VbenAdmin)

- 添加基于 VbenAdmin + Vue3 + Element Plus 的前端管理系统
- 包含完整的 UI 组件库和工具链
- 支持多应用架构 (web-ele, backend-mock, playground)
- 包含完整的开发规范和配置
- 修复 admin 目录的子模块问题，确保正确提交

admin/internal/tsconfig/base.json

@@ -0,0 +1,40 @@
+{
+  "$schema": "https://json.schemastore.org/tsconfig",
+  "display": "Base",
+  "compilerOptions": {
+    "composite": false,
+    "target": "ESNext",
+
+    "moduleDetection": "force",
+    "experimentalDecorators": true,
+
+    "baseUrl": ".",
+    "module": "ESNext",
+
+    "moduleResolution": "node",
+    "resolveJsonModule": true,
+
+    "strict": true,
+    "strictNullChecks": true,
+    "noFallthroughCasesInSwitch": true,
+    "noImplicitAny": true,
+    "noImplicitOverride": true,
+    "noImplicitThis": true,
+    "noUncheckedIndexedAccess": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+
+    "inlineSources": false,
+    "noEmit": true,
+    "removeComments": true,
+    "sourceMap": false,
+    "allowSyntheticDefaultImports": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "isolatedModules": true,
+    "verbatimModuleSyntax": true,
+    "skipLibCheck": true,
+    "preserveWatchOutput": true
+  },
+  "exclude": ["**/node_modules/**", "**/dist/**", "**/.turbo/**"]
+}