i18n: Add Chinese (zh_CN) translations for sqlmap

- Add gettext-based i18n infrastructure (lib/core/i18n.py)
- Add Chinese .po/.mo translation files (1589 strings, fully translated)
- Add Chinese README (zh_README.md)

Translator: Liang Xiangan

Author: gbfdhenr

lib/core/i18n.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+
+"""
+Copyright (c) 2006-2026 sqlmap developers (https://sqlmap.org)
+See the file 'LICENSE' for copying permission
+
+Internationalization (i18n) support using GNU gettext.
+"""
+
+import gettext
+import os
+import sys
+
+_LOCALE_DIR = os.path.join(os.path.dirname(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))), "locales")
+
+_DOMAIN = "sqlmap"
+
+_translation = None
+
+def init(language=None):
+    """
+    Initialize gettext translation.
+    
+    If no language is specified, try to detect from system locale.
+    """
+    global _translation
+
+    if language is None:
+        import locale
+        try:
+            language, _ = locale.getdefaultlocale()
+        except Exception:
+            language = os.environ.get("LANG", "en_US.UTF-8")
+
+    if language:
+        language = language.split(".")[0]  # e.g., "zh_CN.UTF-8" -> "zh_CN"
+
+    try:
+        if language and language != "en_US":
+            _translation = gettext.translation(
+                _DOMAIN,
+                localedir=_LOCALE_DIR,
+                languages=[language],
+                fallback=True
+            )
+        else:
+            _translation = gettext.NullTranslations()
+    except Exception:
+        _translation = gettext.NullTranslations()
+
+    # Install the _() function into builtins so it's available everywhere
+    if isinstance(_translation, gettext.NullTranslations):
+        import builtins
+        builtins.__dict__["_"] = lambda msg: msg
+    else:
+        _translation.install()
+
+
+def _(message):
+    """
+    Translate a message.
+    """
+    global _translation
+    if _translation is None:
+        init()
+    return _translation.gettext(message) if _translation else message