Remove internal project files from repository

- Remove AUFGABEN.txt (internal task list)
- Remove CodeBox_Konzept.md (internal roadmap concept)
- Remove Feature_Analyse_PythonBox.md (internal feature analysis)
- Update .gitignore to exclude internal files and .claude/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Lukas Geiger

.gitignore

@@ -46,3 +46,12 @@ Desktop.ini
 releases/
 *.exe
 *.spec
+
+# Internal project management
+AUFGABEN.txt
+CodeBox_Konzept.md
+Feature_Analyse_PythonBox.md
+desktop.ini
+
+# Claude Code internal
+.claude/