Add code suggestions accepted by user table

What does this MR do and why?

This MR introduces the first iteration of a user metrics table component for AI impact analytics dashboards. The implementation adds functionality to display user-specific AI usage data, including code suggestions accepted and Duo chat interactions.

Problem Being Solved

Analytics dashboards need to display granular user-level metrics for AI features to help teams understand adoption patterns and usage effectiveness across individual contributors.

Changes Made

• Creates new UserLink Vue component with avatar, name, and username display
• Implements user_ai_usage_data data source with GraphQL query support
• Adds user metrics table visualization configuration
• Integrates the table into the AI Impact dashboard
• Adds comprehensive Storybook stories for component testing

References

Screenshots or screen recordings

Screen_Recording_2025-10-17_at_18.07.15

How to set up and validate locally

Key Changes Summary

Component	Action	Purpose
UserLink Vue component	Added	Display user avatars with links in data tables
GraphQL query	Created	Fetch AI user metrics for groups/projects
Data source	Implemented	Bridge GraphQL data to visualization components
Visualization config	Added	Define user metrics table structure and fields
Dashboard integration	Updated	Include user metrics table in AI Impact dashboard

MR acceptance checklist

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Related to #574420