feat: add pie chart visualization for top 5 crowdsourced slurs

[Mahimahto]

Overview

This PR adds a pie chart visualization to the dashboard that displays the top 5 most frequently reported crowdsourced slurs.

What’s Included

• Seed Script for Testing
  Added dummy data using UserContribution.create_crowdsourced_slur_seed/1 in priv/repo/seeds.exs to test the chart effectively.

• Top 5 Slurs Function
  Implemented get_top_5_slurs/0 in the UserContribution module. It:

  • Groups slurs by label
  • Counts their frequency
  • Sorts them in descending order
  • Returns the top 5 in %{label, count} format

• Dashboard Integration

  • Called get_top_5_slurs/0 from DashboardController
  • Assigned the result to @pie_data

• Frontend Integration

  • Embedded @pie_data in the dashboard.html.heex template using Jason.encode!
  • Rendered a pie chart using JavaScript (with either D3.js or native SVG)
  • Automatically draws the chart on DOMContentLoaded

Related Issue

Fixes #777

Sreenshot :-