Fix date formatting and i18n month warnings in BackupsTable

[rahul810050]

Fixed issue: #25

PR Summary

This PR fixes multiple date-related issues in the Backups table.

What was fixed

• Prevents SHARED.DATE.MONTH.undefined vue-i18n warnings by safely resolving month keys.
• Handles missing or invalid end dates gracefully (e.g. backups still in progress).
• Initializes months defensively to avoid access before store hydration.

Changes made

• Added guards before calling $t("SHARED.DATE.MONTH.*").
• Improved formatDate() to handle null/invalid date values.
• UX improvement: replaces "SHA date" with a safe placeholder for ongoing backups.
• added key value for in progress in all the languages

Before:

After: