fix: Prevent Merging Empty Incidents

[AkashJana18]

Closes #3370
/claim #3370

📑 Description

This update enhances the incident merging functionality by introducing stricter validation, improved error handling, and clearer messaging to ensure a more reliable and user-friendly experience. Improves overall system reliability by preventing unintended actions.

Key Changes:

1. Validation Enhancements:

• Prevents merging when no source incidents are selected.
• Ensures the destination incident ID is valid before proceeding.

2. Improved Response Handling:

• Clearly differentiates between merged, skipped, and failed incidents.
• Provides detailed messages for better visibility into the process.

3. Refined User Experience:

• Prevents invalid actions before sending requests.
• Displays more informative success and failure messages.

4. Code Optimizations:

• Streamlined logging for better clarity.
• Reduced redundant processing with early exits.

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

🛠️ How to Test:

1. Attempt merging without selecting source incidents → Should show an error and prevent the action.
2. Merge valid incidents → Should proceed successfully with a confirmation message.
3. Merge incidents where some are invalid → Should provide detailed feedback on skipped/failed incidents.
4. Check responses → The returned messages should align with the UI updates for consistency.

[vercel]

@AkashJana18 is attempting to deploy a commit to the KeepHQ Team on Vercel.

A member of the Team first needs to authorize it.

[talboren]

@AkashJana18 can you add a few screenshots of some use cases and how it looks?