Update German translation

[cantosun99]

Alright, I've deleted all my open PRs and instead bundled them all into one for each language, as per vnepogodin's request. German is done with this one, Russian will follow. I thought this made it more transparent to see what I did with each file, but it really only made a mess of the PR list.

I've also looked into what on earth went wrong with the German sched-ext.mdx and I found out my mistake:

The file was one of the last ones that had to be translated because it had nearly 15 commits since the last update and I wanted to finish the easy stuff first. Before, I translated the files commit by commit so translate everything that has been done in one commit, move to the next commit and so on. For this file with its huge number of commits with a big portion of them overwriting themselves, this just wasn't sensible. Instead I decided to manually copy the contents of the currently live English file and the currently live German one into a temporary document and just translate from there. Now that's where we get to the problem: I copied the contents of the damn secure_boot_setup.mdx files. After finishing the translation in the temporary document, I copied the content into the sched-ext.mdx file, tested it in bun, looked fine, committed it. I guess I was so into the "stop thinking and just translate" mindset that I just saw "ah, file starting with the letter s, gonna translate that".

Now, I'm not looking to provide excuses, I just wanted to clarify what happened. Maybe it's no big deal to you, maybe it is, fact is, I made two mistakes that I'm embarrassed about so I wanted to apologize. First, I apologize to @vnepogodin for spamming a lot of PRs when I could just bundle them into one and second I apologize to @Aarrayy that I made such a stupid mistake with copying and translating the wrong file, good catch on your part. I promise to be more considerate and careful in the future.

I hope you understand that I just want to help but wasn't aware of the etiquette for PRs and made a stupid autopilot-mistake, thank you.

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This PR bundles the currently needed changes for the German translation.

• post_install_setup.mdx: I deleted PR 585 and bundled it here. It updates the file to the current English version with all the changes made since the 26th of January.
• astro.config.mjs: I deleted PR 586 and bundled it here. It fixes the old German translations in the side-bar being off like "Post Install Recommendations" being translated to "Post Install Guessing" and adds a few missing ones.
• sched-ext.mdx: I translated the right file this time. Man, that's embarrassing. It updates the file to the current English version with all the changes made since the 30th of January.
• enabling_hardware_acceleration_in_google_chrome.mdx: I went through my previous PRs to make sure I didn't make another mistake like the sched-ext one and noticed that in this file I forgot to change the title back from English, the rest is fine.
• hyprland.mdx: Regular update to the German translation.

[Aarrayy]

It's okay, don't worry. my bad for not noticing too