新增：管理后台前端页面，以及openspec内容。

openspec/changes/fix-frontend-issues/tasks.md

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+## 1. Fix Theme Store Initialization Order
+- [x] 1.1 Initialize Pinia before using themeStore in main.js
+- [x] 1.2 Verify that the `ReferenceError: Cannot access 'themeStore' before initialization` error is resolved
+
+## 2. Fix Sass @import Deprecation Warnings
+- [x] 2.1 Replace @import with @use in main.scss for variables.scss
+- [x] 2.2 Replace @import with @use in main.scss for responsive.scss
+- [x] 2.3 Verify that no Sass deprecation warnings appear during build
+
+## 3. Add Best Practices Documentation
+- [x] 3.1 Create implementation.md with best practices for frontend development
+- [x] 3.2 Document the importance of store initialization order
+- [x] 3.3 Document the use of @use instead of @import for Sass files
+
+## 4. Verification
+- [x] 4.1 Run build command to verify no warnings or errors
+- [x] 4.2 Test application functionality to ensure no regressions