Move normalize_hostname to helpers to break circular import

Importing from sinks.socket in vulnerabilities.ssrf.imds created a
cycle through sinks.socket.__init__ → aikido_zen.vulnerabilities.
Move the implementation to helpers/normalize_hostname.py and have
sinks/socket/normalize_hostname.py re-export from there.

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

Author: bitterpanda63

aikido_zen/helpers/normalize_hostname.py

@@ -0,0 +1,14 @@
+def normalize_hostname(hostname):
+    if not hostname or not isinstance(hostname, str):
+        return hostname
+
+    # Lowercase and strip trailing dot (DNS resolvers may return FQDNs like "example.com.")
+    result = hostname.lower().rstrip(".")
+
+    try:
+        # Decode Punycode if the hostname starts with xn--
+        if result.startswith("xn--"):
+            result = result.encode("ascii").decode("idna")
+        return result
+    except (UnicodeError, LookupError):
+        return result

aikido_zen/sinks/socket/normalize_hostname.py

@@ -1,14 +1,3 @@
-def normalize_hostname(hostname):
-    if not hostname or not isinstance(hostname, str):
-        return hostname
+from aikido_zen.helpers.normalize_hostname import normalize_hostname
 
-    # Lowercase and strip trailing dot (DNS resolvers may return FQDNs like "example.com.")
-    result = hostname.lower().rstrip(".")
-
-    try:
-        # Decode Punycode if the hostname starts with xn--
-        if result.startswith("xn--"):
-            result = result.encode("ascii").decode("idna")
-        return result
-    except (UnicodeError, LookupError):
-        return result
+__all__ = ["normalize_hostname"]

aikido_zen/vulnerabilities/ssrf/imds.py

@@ -4,7 +4,7 @@
 """
 
 from aikido_zen.helpers.ip_matcher import IPMatcher
-from aikido_zen.sinks.socket.normalize_hostname import normalize_hostname
+from aikido_zen.helpers.normalize_hostname import normalize_hostname
 
 imds_addresses = IPMatcher(
     [