Summary

Closes #681

Changes Made

• Introduced partially Optimistic Updates
• Deleted duplicates in the state (itemsByState, itemsByHash)
• Replaced localItem logic with React Query mutations and refetching.
• Removed obsolete constants associated with localItem and silence states.
• Deleted client.js, AltertmangerAPI, scheduledSilencesWrapper and apiService, as their responsibilities have been migrated to React Query or other parts of the code.
• Updated modal handling to ensure they close where appropriate, streamlining user interactions.
• This refactor simplifies state management, reduces redundancy, and leverages React Query’s capabilities for a cleaner, more maintainable codebase.

Testing Instructions

1. npm i
2. npm run TASK

Checklist

• I have performed a self-review of my code.
• I have commented my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• I have made corresponding changes to the documentation (if applicable).
• My changes generate no new warnings or errors.