chore: set plugin author to Daniel Kastl

The plugin metadata still credited 'Georepublic'. Set the current author
to Daniel Kastl (github.com/dkastl), the plugin's creator and maintainer.
Historical authorship remains in the git history.

Author: dkastl

init.rb

@@ -7,8 +7,8 @@
 Redmine::Plugin.register :redmine_gtt_fiware do
   # Plugin metadata
   name 'Redmine GTT FIWARE plugin'
-  author 'Georepublic'
-  author_url 'https://github.com/georepublic'
+  author 'Daniel Kastl'
+  author_url 'https://github.com/dkastl'
   url 'https://github.com/gtt-project/redmine_gtt_fiware'
   description 'Adds FIWARE integration capabilities for GTT projects'
   version '2.0.1'