Write only the initial year in copyright notices

Updating the range of years in copyright notices is tedious and often forgotten. [REUSE](https://reuse.software/faq/#years-copyright) says it's fine to only show the initial year, and I think the Go project does that as well.\ Here is [an example](https://github.com/golang/go/blob/master/src/archive/tar/common.go) of Go's copyright notice: it shows the year 2009, when this file was created, and here [another example](https://github.com/golang/go/blob/45138d477d5a7547086357218061429d3c80a6be/src/runtime/time_plan9.go#L1) with year 2025. I propose to show only the year of creation of a file to ease maintenance. ### Open questions: - Can we replace the copyright notice for already existing files? - Apparently, yes. Daniel Stenberg of cURL fame [did it](https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/). See [his commit](https://github.com/curl/curl/commit/2bc1d775f510196154283374284f98d3eae03544) on the matter. - From [this message](https://github.com/AerynOS/os-tools/issues/714#issuecomment-3958156216): since we renamed the project from SerpentOS to AerynOS, do we need TWO copyright lines or can we just edit the notice? - [According to the US Patent Office](https://www.uspto.gov/trademarks/basics/trademark-patent-copyright), copyright is not assigned to names but to *contents*. I'm inclined to say that we can just edit the existing copyright notice, because copyright holders didn't change.