pyproject.toml: Enable mypy.disallow_untyped_calls

Add disallow_untyped_calls = true to the mypy configuration. This
requires all function calls from typed code to target typed functions,
ensuring better type safety across the codebase.

Assisted-by: unsloth/Qwen3.6-35B-A3B-GGUF:IQ4_NL and pi.dev 0.81.1
Signed-off-by: Jan Lindemann <jan@janware.com>

conf/templates/pyproject.toml

@@ -12,6 +12,8 @@
 
   warn_unreachable = true
 
+  disallow_untyped_calls = true
+
   enable_error_code = [
     "explicit-override",
     "ignore-without-code",