fix(newfile): await local storage promise to prevent data corruption

[vibhutomer]

Fix: Prevent Metadata Corruption on Auto-Save

Related Issue

• Closes Unresolved Promise Causes Data Corruption on Auto-Save #73

Description of Changes

• In NewFile.tsx, the newFile() handler was executing a synchronous read on an asynchronous Local Storage API.
• Converted newFile() to an async function.
• Added the await keyword to props.store._getFile(props.file) to properly resolve the file metadata before constructing the updated File object.

Impact

• Data Integrity: Prevents the file's created timestamp from being overwritten with undefined when the user opens a new workspace.
• Reliability: Ensures that local storage operations complete sequentially, preventing race conditions between reading the old file and loading the default template.