Translate new landing to Danish

[mikini]

i18n/locales/da.yaml:

• everything done except social_callout_*
• keep English source as comments for reference in case of
  future source changes

content/pages/da/index.md:

• update "advanced flow" section with flow details from 2026-03

[marcprux]

Thanks! Please verify that it looks OK: https://keepandroidopen.org/da/

[mikini]

Thanks! Please verify that it looks OK: https://keepandroidopen.org/da/

There's a few typos and minor corrections that I'll want to fix.

Also, it seems that the new landing's advanced flow description mistakenly says to go to developer settings to enable developer settings (see official guide).
The /cta page correctly says to go to "About Phone", and also includes the missing step between 2 & 3 to actually go to Developer settings after enabling it and activating "Allow Unverified Packages" (is this a speculative menu item, I have not been able to verify this from any of Google's communication?).

I guess all this is still hypothetical, so correctness might not be all that important, point is to show that it is an elaborate procedure. I have, however fixed the wrong menu item in the first step in PR #463 both for Danish and English. Let me know if you prefer separating English/Danish changes or if I am otherwise wrong about this.