feat:added severity badge in event row and remove payload from event api

[Adarsh9977]

Summary

• Add latest verdict metadata to the event list API response without including heavy event payload or token fields.
• Show severity badges in the Events table and mobile cards based on MAD codes.
• Keep the event list API lightweight by omitting full payload/token fields from list rows, while still loading full event details on demand when a row is expanded.

Test plan

• Added backend coverage confirming event list items omit payload/token fields and include latest verdict data.

Screenshot (UI changes only)

Checklist

• CLA signed (see CLA.md)
• Tests pass locally
• Docs updated where needed
• British English; no em-dashes; no marketing fluff