i18n: migrate all German text to English

Enforce the repo convention that committed text is English.
Translates ABOUTME headers, code comments, log/error messages,
shell prompts, and documentation across all files.
CLAUDE.md files remain in German per policy.

config/user_configuration.json

@@ -1,6 +1,6 @@
 {
-    "__comment": "ABOUTME: archinstall-Konfiguration für Moonarch.",
-    "__comment2": "ABOUTME: Basis-Setup — Kernel, Disk und Filesystem werden interaktiv gewählt.",
+    "__comment": "ABOUTME: archinstall configuration for Moonarch.",
+    "__comment2": "ABOUTME: Base setup — kernel, disk and filesystem are chosen interactively.",
 
     "audio_config": {
         "audio": "pipewire"