fix(report): render ECharts fence aliases in HTML

[March-77]

Describe what this PR does / why we need it

HTML report exports only recognize ECharts options fenced as echarts or json. Models also commonly emit the same option as javascript or js; those blocks are currently rendered as raw code, leaving chart configuration text in the exported report.

Does this pull request fix one issue?

Fixes #416

Describe how you did it

• Normalize fence languages before dispatching code blocks.
• Treat javascript and js as ECharts aliases alongside echarts and json.
• Keep the backend download template and frontend HTML preview template consistent.
• Add backend and frontend regression tests.

Describe how to verify it

JAVA_HOME=<jdk17> ./mvnw -pl data-agent-management -Dtest=ReportTemplateUtilTest test
JAVA_HOME=<jdk17> ./mvnw -pl data-agent-management test
cd data-agent-frontend-nuxt
pnpm exec vitest run app/utils/report-html-template.test.ts
pnpm build

Results: backend template tests 5/5 passed; full management module 1630/1630 passed; frontend test passed; Nuxt production build passed; Checkstyle reported 0 violations.

Special notes for reviews

The report prompt still requests the canonical echarts language. This change only makes HTML rendering tolerant of common model output aliases.

[March-77]

用同一份 javascript fence 的 ECharts 配置做了对比。main（7a4d03a）会把配置作为代码显示；308cafe 会识别该别名并渲染图表。前端回归测试 1/1 通过。

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After：