feat(middleware): add DataMaskingMiddleware — sensitive entity protection (Chunk 3)

Priority 90 — runs before Compaction@100 and Memory@150.
Detects and replaces company names, money amounts, phone numbers,
emails, and ID card numbers with deterministic tokens (__ENTITY_N__).
External callers can restore originals via DataMasker::unmask().

crates/zclaw-runtime/src/middleware.rs

@@ -267,6 +267,7 @@ impl Default for MiddlewareChain {
 
 pub mod compaction;
 pub mod dangling_tool;
+pub mod data_masking;
 pub mod guardrail;
 pub mod loop_guard;
 pub mod memory;