macOS Time Machine AFP monitoring: backup_time update on file modification

- Added afp_monitor.rs module to track AFP_AfpInfo backup_time
- Open struct now has 'modified' flag to track file modifications
- write.rs sets modified=true on successful write
- close.rs calls AfpMonitor::update_backup_time() on modified files
- create.rs calls AfpMonitor::init_afp_info() on new file creation
- AFP_AfpInfo stored as xattr com.apple.aapl.AfpInfo
- backup_time updated to current epoch time on modification

Also includes:
- LZ4 compression using lz4_flex crate
- Case sensitivity conditional on backend capabilities
- LDAP cfg feature gate fix
- RAID rebuild reconstruction implementation
- DOS attributes xattr persistence
- Snapshot disk persistence

Tests: 201 smb-server, 452 markbase-core (653 total)

vendor/smb-server/Cargo.toml

@@ -24,7 +24,8 @@ md4 = "0.10"
 aes = "0.8"
 cmac = "0.7"
 rc4 = "0.2"
-ctr = "0.9"  # AES-CTR for SMB3 encryption (simplified approach)
+aes-gcm = "0.10"
+ccm = "0.5"
 xattr = "1.0"  # Extended attributes support (AFP_AfpInfo)
 
 [features]