Change: Update dependencies and require Go 1.25 or newer

Dependencies have been updated. Building restic now requires Go 1.25 or newer.
The Windows build with Go 1.26 was also fixed.

https://github.com/restic/restic/issues/21791
https://github.com/restic/restic/pull/5619
https://github.com/restic/restic/pull/21796