feat(security): migrate content scanning and bounce detection to Rust security bridge; add scanContent IPC command and Rust content scanner with tests; update TS RustSecurityBridge and callers, and adjust CI package references

rust/crates/mailer-security/src/lib.rs

@@ -1,5 +1,6 @@
 //! mailer-security: DKIM, SPF, DMARC verification, and IP reputation checking.
 
+pub mod content_scanner;
 pub mod dkim;
 pub mod dmarc;
 pub mod error;