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/src/handlers/write.rs

@@ -102,6 +102,13 @@ pub async fn handle(
         Ok(n) => n,
         Err(e) => return HandlerResponse::err(e.to_nt_status()),
     };
+    
+    // AFP monitoring: Set modified flag for Time Machine backup tracking
+    {
+        let mut open = open_arc.write().await;
+        open.modified = true;
+    }
+    
     let mut buf = Vec::new();
     WriteResponse::new(count)
         .write_to(&mut buf)