feat: migrate INWX DNS CLI to interactive Textual TUI

- replace CLI menu with multi-panel Textual interface (sidebar & data table)
- implement asynchronous loading for domains and DNS records via worker threads
- add support for optional 2FA/TOTP auto-unlock and manual TAN modal
- introduce .env configuration fallback for stored credentials
- add modals for creating, editing, and deleting DNS records
- enable inline row editing via mouse double-click and keyboard navigation
- update project documentation in README.md

main.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python3
+"""INWX DNS TUI Client
+Author:  Pascal Bouquet <pascal@ptbos.de>
+License: GNU General Public License v3.0 (GPL-3.0)
+Year:    2026
+"""
+
+import sys
+from tui_app import InwxTUIApp
+
+def main():
+    app = InwxTUIApp()
+    try:
+        app.run()
+    except KeyboardInterrupt:
+        sys.exit(0)
+
+if __name__ == "__main__":
+    main()