Enable writeback_cache and async_dio FUSE options (#7980)

* Enable writeback_cache and async_dio FUSE options

Fixes #7978

- Update mount_std.go to use EnableWriteback and EnableAsyncDio from go-fuse
- Add go.mod replace directive to use local go-fuse with capability support
- Remove temporary workaround that disabled these options

This enables proper FUSE kernel capability negotiation for writeback cache
and async direct I/O, improving performance for small writes and concurrent
direct I/O operations.

* Address PR review comments

- Remove redundant nil checks for writebackCache and asyncDio flags
- Update go.mod replace directive to use seaweedfs/go-fuse fork instead of local path

* Add TODO comment for go.mod replace directive

The replace directive must use a local path until seaweedfs/go-fuse#1 is merged.
After merge, this should be updated to use the proper version.

* Use seaweedfs/go-fuse v2.9.0 instead of local repository

Replace local path with seaweedfs/go-fuse v2.9.0 fork which includes
the writeback_cache and async_dio capability support.

* Use github.com/seaweedfs/go-fuse/v2 directly without replace directive

- Updated all imports to use github.com/seaweedfs/go-fuse/v2
- Removed replace directive from go.mod
- Using seaweedfs/go-fuse v2.0.0-20260106181308-87f90219ce09 which includes:
  * writeback_cache and async_dio support
  * Corrected module path

* Update to seaweedfs/go-fuse v2.9.1

Use v2.9.1 tag which includes the corrected module path
(github.com/seaweedfs/go-fuse/v2) along with writeback_cache
and async_dio support.

weed/command/mount_std.go

@@ -18,7 +18,7 @@ import (
 
 	"github.com/seaweedfs/seaweedfs/weed/util/version"
 
-	"github.com/hanwen/go-fuse/v2/fuse"
+	"github.com/seaweedfs/go-fuse/v2/fuse"
 	"github.com/seaweedfs/seaweedfs/weed/glog"
 	"github.com/seaweedfs/seaweedfs/weed/mount"
 	"github.com/seaweedfs/seaweedfs/weed/mount/meta_cache"
@@ -216,12 +216,8 @@ func RunMount(option *MountOptions, umask os.FileMode) bool {
 		fuseMountOptions.Options = append(fuseMountOptions.Options, fmt.Sprintf("iosize=%d", ioSizeMB*1024*1024))
 	}
 
-	if option.writebackCache != nil && *option.writebackCache {
-		fuseMountOptions.Options = append(fuseMountOptions.Options, "writeback_cache")
-	}
-	if option.asyncDio != nil && *option.asyncDio {
-		fuseMountOptions.Options = append(fuseMountOptions.Options, "async_dio")
-	}
+	fuseMountOptions.EnableWriteback = *option.writebackCache
+	fuseMountOptions.EnableAsyncDio = *option.asyncDio
 	if option.cacheSymlink != nil && *option.cacheSymlink {
 		fuseMountOptions.EnableSymlinkCaching = true
 	}