docs: Version 1.2.1, Dokumentation und Man-Page aktualisieren

- Versionsnummer auf 1.2.1 hochgesetzt
- Man-Page: NO_COLOR Umgebungsvariable dokumentiert (ENVIRONMENT-Abschnitt)
- Man-Page: Konfigurationsreihenfolge mit Prioritäten korrigiert
- Man-Page: --no-color Beschreibung um NO_COLOR-Referenz ergänzt
- README: Hilfe-Ausgabe aktualisiert (fehlende Optionen: -r, --max-depth,
  -s, -L, --conf, --no-color)
- README: NO_COLOR Hinweis in deutsch und englisch ergänzt

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

man/ntu.1

@@ -1,4 +1,4 @@
-.TH NTU 1 "2025-02-12" "NameToUnix 1.2.0" "User Commands"
+.TH NTU 1 "2026-02-13" "NameToUnix 1.2.1" "User Commands"
 .SH NAME
 ntu \- sanitize file and directory names to Unix conventions
 .SH SYNOPSIS
@@ -55,7 +55,8 @@ Allow renaming of the root directory itself (normally skipped)
 Process symbolic links and special files (normally skipped)
 .TP
 .BR \-\-no\-color
-Disable colored output
+Disable colored output. The \fBNO_COLOR\fR environment variable is also
+respected (see \fIhttps://no-color.org/\fR).
 .TP
 .BR \-h ", " \-\-help
 Print help information
@@ -180,18 +181,28 @@ Symlinks are still not followed (targets remain unchanged)
 Safe: only the link itself is renamed, not what it points to
 .SH CONFIGURATION
 .B ntu
-looks for configuration files in the following locations (in order):
+looks for configuration files in the following locations. Later files
+override earlier ones (highest priority last):
 .PP
 .nf
 .RS
-./.NameToUnix.conf
-~/.config/NameToUnix/config.toml
-/etc/NameToUnix/config.toml
+1. /etc/NameToUnix/config.toml    (system-wide, lowest priority)
+2. ~/.config/NameToUnix/config.toml  (user-specific)
+3. ./.NameToUnix.conf             (working directory, highest priority)
 .RE
 .fi
 .PP
-Configuration files can customize character replacements and other behavior.
-See the project documentation for configuration file format.
+When using \fB\-\-conf\fR, the standard hierarchy is bypassed and only the
+specified file is loaded.
+.PP
+Configuration files use TOML format with a \fB[replacements]\fR section
+for custom character replacements. See the project documentation for details.
+.SH ENVIRONMENT
+.TP
+.B NO_COLOR
+When set (to any value), colored output is disabled. This follows the
+convention described at \fIhttps://no-color.org/\fR. The \fB\-\-no\-color\fR
+flag has the same effect.
 .SH EXIT STATUS
 .TP
 .B 0