refactor(mermaid): performance optimization and support pan and zoom etc. (#737)

* perf(mermaid): optimize rendering by deferring non-critical tasks and enhancing viewport observation

* feat(mermaid): add panzoom and download svg actions for mermaid

* feat(mermaid): enhance diagram controls and add fullscreen action for code tabs

* feat(i18n): update translation keys for diagram and tab actions in multiple languages

* fix(mermaid): move mermaid-neutral inside diagram-container in wrapper mode

Agent-Logs-Url: https://github.com/hugo-fixit/FixIt/sessions/e79e837e-be0b-445c-8bd3-8c03cdce2651

Co-authored-by: Lruihao <33419593+Lruihao@users.noreply.github.com>

* fix(mermaid): update download filename for SVG export in diagram controls

* refactor(mermaid): refactor rendering logic and enhance task queue for improved performance

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

.github/copilot-instructions.md

@@ -85,7 +85,6 @@ FixIt/
 
    ```scss
    @include border-radius;
-   @include transition(all 0.2s ease);
    ```
 
 ### 代码质量要求