Add Security Audit Phase 9: comprehensive SSH security tests

- auth_security: password brute force, public key, user status, home dir
- crypto_security: AES-CTR, HMAC-SHA256, Curve25519, Ed25519
- file_access_security: path traversal, absolute path, symlink attack
- channel_security: window limits, request validation
- 18 new security tests, all pass (153 total)

markbase-core/src/lib.rs

@@ -26,6 +26,9 @@ pub mod sync;
 pub mod provider;  // DataProvider抽象层（Phase 5）
 pub mod vfs;  // VFS抽象层（Phase 1-6重构计划）
 
+#[cfg(test)]
+mod security_audit;  // Security Audit Module - Phase 9
+
 // Re-export from external filetree crate
 pub use filetree::node::FileNode;
 pub use filetree::FileTree;