feat: performance optimizations

[therobrob]

I’ve experimented with some performance optimizations. Feel free to have a critical view. :)

• merged pagefind implementations, because we already overwrite an large part of it. Copilot helped me to reorder the file.
• there was an issue regarding our fonts, which weren’t loaded with font-swap. So i’ve added it and Metric Overrides to avoid layout shifts
• the hero-image wasn’t loaded with fetchpriority=high
• there was an issue with chaining critital requests. I’ve added the defer property to the js.

[github-actions]

Hi there! 👋

Thank you for your contribution to the FIP Guide! 🚀
We appreciate your effort in making rail staff travel information more accessible. 🚄

Checklist before merging:

• Added a description to the Pull Request
• Checked the License of new pictures (non-commercial use without attribution)
• Modified content in English
• Modified content in German
• Modified content in French

[netlify]

✅ Deploy Preview for fipguide ready!

Name	Link
🔨 Latest commit	b5f7174
🔍 Latest deploy log	https://app.netlify.com/projects/fipguide/deploys/69600cfe28eb5a0008533913
😎 Deploy Preview	https://deploy-preview-551--fipguide.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[therobrob]

Unfortunately, there is an error: Uncaught ReferenceError: PagefindUI is not defined.

[MoritzWeber0]

Thanks for the effort to merge the pagefind styles 🚀
It's great if we no longer have to load thepagefind-ui CSS file :)
Unfortunately, there are a few styling issues when I run it locally, not sure if it's just my local preview that has those issues. I added comments for each issue that I found, sorry for the amount 😅

Wanted to approve the other PR, I should get some sleep xD