fix: properly await all async operations and add error handling

[shivv23]

Summary

This PR fixes all missing await keywords and unhandled Promise rejections across the codebase. Several async operations were called without await, causing data corruption, silent failures, and unhandled Promise rejections.

Critical Bugs Fixed

File	Issue	Impact
Menu.tsx doSave()	_getFile() called without await — data was a Promise object, so .created was undefined	File constructed with corrupted metadata
Menu.tsx doSave()	_saveFile() called without await — save could silently fail	User sees "success" even when data is lost
NewFile.tsx newFile()	Same _getFile() and _saveFile() missing await	Same data corruption + silent failure
Files.tsx delete handler	_deleteFile() called without await	Delete can silently fail; UI refreshes before deletion completes

Changes by File

Menu.tsx

• doSave(): Made async, added await to both _getFile() and _saveFile(), added try/catch
• doSaveAs(): Added await before _saveFile(), wrapped in try/catch
• doPrint(): Made async, added await to printer.print(), added try/catch
• sendEmail(): Made async, added await to EmailComposer.open(), added try/catch

NewFile.tsx

• newFile(): Made async, added await to _getFile() and _saveFile(), added try/catch

Dashboard.tsx

• useEffect: Added .catch() to loadData() call to handle unhandled rejections
• handleOpen(): Converted from .then() chain (with no .catch()) to async/await with try/catch
• Added await to all 5 loadData() calls inside async handlers (handleBackup, handleRestore, handleShare, confirmDelete, handleNewFile)

Files.tsx

• editFile(): Converted from .then() chain (with no .catch()) to async/await with try/catch
• Delete handler: Made async, added await to _deleteFile() and loadFiles(), added try/catch
• Added await to loadFiles() calls in handleBackup and handleRestore

BackupSuccessModal.tsx

• Added console.warn to previously empty catch block in copyToClipboard

Verification

• npx tsc --noEmit passes with zero new errors (only pre-existing @meshkit/ionic module stub error)