fix(desktop): restore WriteAt trait import dropped by PR#50 port

ticket::FetchData::write_at is a utility::WriteAt trait method on
Windows; the upstream PR removed the import since the non-Windows stub
provides write_at inherently. Gated the import to cfg(windows).

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desktop/crates/cloudreve-sync/src/drive/commands.rs

@@ -13,6 +13,8 @@ use crate::{
     tasks::TaskPayload,
     utils::toast,
 };
+#[cfg(windows)]
+use crate::cfapi::utility::WriteAt;
 use anyhow::{Context, Result};
 use bytes::Bytes;
 use cloudreve_api::{