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.

packages/aur.txt

@@ -1,7 +1,7 @@
-# ABOUTME: Liste der AUR-Pakete, die nach der Basisinstallation via paru installiert werden.
-# ABOUTME: Wird von post-install.sh verwendet.
+# ABOUTME: List of AUR packages installed via paru after the base installation.
+# ABOUTME: Used by post-install.sh.
 
-# AUR Helper (wird zuerst manuell gebaut)
+# AUR Helper (built manually first)
 # paru
 
 # Theming
@@ -18,7 +18,7 @@ wl-color-picker
 wlogout
 gtklock-dpms-module
 
-# Anwendungen
+# Applications
 blueberry
 waterfox-bin