fix(types): P0 mypy — explicit binascii import, drop dead or None in ntlmssp

syslog_bridge.py: base64.binascii is not a public mypy-visible attribute;
import binascii directly and reference binascii.Error at the except clause.
Propagated to all 26 template subdirectory copies (all were drift-free).

ntlmssp.py: `principal = username or None` widened the type to str | None
for no runtime reason — _decode_str() always returns str.  Drop the `or None`.
Propagated to smb/ and rdp/ copies.

762 → 722 mypy errors (-40).

decnet/templates/_shared/ntlmssp.py

@@ -120,7 +120,7 @@ def parse_type3(blob: bytes) -> Optional[dict]:
     if domain:
         principal = f"{domain}\\{username}"
     else:
-        principal = username or None
+        principal = username
 
     return {
         "username": username,