fix!: create IPC socket in user runtime directory (#1313)

Each user has their own runtime directory at `/run/user/<uid>`. Creating
the IPC socket in there makes sure it is cleaned up regardless of
whether `ncspot` exits normally.

BREAKING CHANGE: move IPC socket location

CHANGELOG.md

@@ -16,6 +16,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Improve error messages generated by the command line
 - Build with crossterm terminal backend by default
+- Move UNIX IPC socket from the user's cache path to the user's runtime directory
 
 ### Fixed