Implement WebDAV VFS integration: dav-server 0.11 compatible

- Add webdav.rs module: VfsDavFs, VfsDavFile, VfsDavMetaData
- Implement DavFileSystem + Clone for GuardedFileSystem blanket impl
- Add clone_boxed to VfsBackend trait (required for Sync)
- Update CLI webdav.rs to use VFS instead of SQLite
- Add bytes dependency
- All 155 tests pass

markbase-core/src/cli/interface/webdav.rs

@@ -1,5 +1,8 @@
 use axum::{extract::Request, response::IntoResponse, Extension};
 use clap::Subcommand;
+use dav_server::{fakels::FakeLs, DavHandler};
+use std::path::PathBuf;
+use std::sync::Arc;
 
 #[derive(Subcommand)]
 pub enum WebdavCommand {
@@ -15,22 +18,22 @@ pub enum WebdavCommand {
 pub async fn handle_webdav_command(cmd: WebdavCommand) -> anyhow::Result<()> {
     match cmd {
         WebdavCommand::Start { port, user } => {
-            let db_path = std::path::PathBuf::from(crate::FileTree::user_db_path(&user));
+            let home_dir = PathBuf::from("/Users/accusys/momentry/var/sftpgo/data").join(&user);
 
-            if !db_path.exists() {
+            if !home_dir.exists() {
                 return Err(anyhow::anyhow!(
-                    "User database not found: {}",
-                    db_path.display()
+                    "User home directory not found: {}",
+                    home_dir.display()
                 ));
             }
 
-            println!("=== MarkBase WebDAV Server ===");
+            println!("=== MarkBase WebDAV Server (VFS) ===");
             println!("User: {}", user);
             println!("Port: {}", port);
-            println!("Database: {}", db_path.display());
+            println!("Home: {}", home_dir.display());
             println!();
 
-            run_webdav_server(port, user, db_path).await?;
+            run_webdav_server(port, home_dir, user).await?;
         }
     }
     Ok(())
@@ -38,14 +41,22 @@ pub async fn handle_webdav_command(cmd: WebdavCommand) -> anyhow::Result<()> {
 
 async fn run_webdav_server(
     port: u16,
+    home_dir: PathBuf,
     user: String,
-    db_path: std::path::PathBuf,
 ) -> anyhow::Result<()> {
-    use axum::{routing::any, Extension, Router};
+    use axum::{routing::any, Router};
     use tokio::net::TcpListener;
 
-    let webdav = markbase_webdav::webdav::MarkBaseWebDAV::new(user, db_path);
-    let dav_handler = webdav.create_handler();
+    let vfs = Box::new(crate::vfs::local_fs::LocalFs::new());
+    let upload_hook = None;
+
+    let dav_fs = crate::webdav::VfsDavFs::new(vfs, home_dir, upload_hook, user);
+
+    let dav_handler = DavHandler::builder()
+        .filesystem(dav_fs)
+        .locksystem(FakeLs::new())
+        .strip_prefix("/webdav")
+        .build_handler();
 
     let app = Router::new()
         .route("/webdav", any(handle_dav))
@@ -67,7 +78,7 @@ async fn run_webdav_server(
 }
 
 async fn handle_dav(
-    Extension(dav): Extension<dav_server::DavHandler>,
+    Extension(dav): Extension<DavHandler>,
     req: Request,
 ) -> impl IntoResponse {
     dav.handle(req).await