#623 Cython optimization: apps/executor.py _sanitize_for_log()

**Target:** engine/apps/executor.py - _sanitize_for_log() method **Expected Gain:** 30-40% **Bottleneck Analysis:** - Called on every app execution - Recursive dict/list traversal with type checking - String slicing operations in loops - Deep nested structure sanitization **Cython Strategy:** - Use typed recursion with cdef functions - C-level type checking (PyDict_Check, PyList_Check) - Optimize string truncation with typed buffers - Inline recursive calls where possible Tags: cython, performance