chore(about): 🔗 Update official website URL to https://markdown.fit

[jorben]

Summary

• Update the website button link in About page from GitHub repo URL to the new official website https://markdown.fit
• Update corresponding test assertion to match the new URL

Test Plan

• Verify "Website" button in About page opens https://markdown.fit
• Run About component tests: npx vitest run src/renderer/components/__tests__/About.test.tsx --config vitest.config.renderer.ts

🤖 Generated with Claude Code

[github-actions]

Summary

This PR updates the About page’s Website button target from the GitHub repository URL to the new official site and aligns the component test accordingly. The change is small, consistent, and appears correct. I don’t see any blocking issues; this is ready to merge.

Praise

• src/renderer/components/About.tsx:53 — UI behavior updated at the source of truth: The button link is changed directly where the action is triggered, keeping behavior explicit and easy to audit.
• src/renderer/components/__tests__/About.test.tsx:130 — Test contract updated with implementation: The assertion was updated in lockstep with the new URL, preventing stale test expectations and preserving confidence in click behavior.