Add first-class Go hosting docs

[davidfowl]

Summary

• Replace the deprecated CommunityToolkit Go hosting page with first-class Aspire.Hosting.Go guidance.
• Cover AddGoApp / addGoApp, app directories and package paths, app arguments, module helpers, Delve debugging, publish behavior, private modules, and experimental Go templates.
• Keep the PR scoped to src/frontend/src/content/docs/integrations/frameworks/go-apps.mdx on release/13.4.

Validation

• pnpm --dir .\src\frontend exec prettier --check src/content/docs/integrations/frameworks/go-apps.mdx
• git diff --check
• pnpm --dir .\src\frontend run check-data
• pnpm --dir .\src\frontend run test:unit:docs

Note: pnpm --dir .\src\frontend run lint currently fails on release/13.4 in tests/unit/llms-txt-twoslash.vitest.test.ts with existing @typescript-eslint/no-unsafe-* errors unrelated to this docs page.

[davidfowl]

cc @edmondshtogu