feat: Migrate to Shadcn/ui, add Contributor Insights, and fix errors

This commit includes a major overhaul of your GitHub Analytics dashboard.

Key changes:

1.  **Error Handling:**
    *   I fixed the "org doesn't exist" error by improving backend API responses (returning 404 for not found orgs) and refining frontend error display to be more specific.

2.  **UI Migration to Shadcn/ui and Tailwind CSS:**
    *   I removed Material UI and all its dependencies.
    *   I installed and configured Tailwind CSS and Shadcn/ui.
    *   I converted the main application layout and page structure to use Tailwind CSS and Shadcn theming (backgrounds, typography, etc.).
    *   I rebuilt all core UI components using Shadcn/ui components and/or custom Tailwind styling:
        *   Organization Input Form (Input, Button, Label)
        *   Stats Cards (Card)
        *   Error Message Display (Card)
        *   Repositories Table (Table)
        *   Activity Timeline (custom Tailwind, Card)
    *   I integrated Recharts for data visualization:
        *   Top Repositories Chart (Bar Chart)
        *   Issues Overview Chart (Pie Chart)
        *   Stars Over Time Chart (Line Chart with simulated data)
        *   Commit Activity Chart (Bar Chart with simulated data)
        *   All charts are styled to align with the Shadcn theme using CSS variables.

3.  **New Feature: Top Contributors:**
    *   Backend: I extended the `/api/github` route to accept a `type=contributors` parameter. This new functionality fetches contributor data for the top N repositories of an organization, aggregates it, caches it, and returns a sorted list of contributors.
    *   Frontend:
        *   I added a `TopContributorsList` component to display avatars, names (linked to GitHub profiles), total contributions, and repositories contributed to.
        *   I modified the main page to fetch contributor data in parallel with repository data and display it in a new "Top Contributors" card.

Your application now has a modern aesthetic, improved error handling, and enhanced analytics capabilities with the new Top Contributors feature. This sets a solid foundation for further feature development.

Author: google-labs-jules[bot]

components.json

@@ -0,0 +1,17 @@
+{
+  "$schema": "https://ui.shadcn.com/schema.json",
+  "style": "default",
+  "rsc": true,
+  "tsx": true,
+  "tailwind": {
+    "config": "tailwind.config.js",
+    "css": "src/app/globals.css",
+    "baseColor": "slate",
+    "cssVariables": true,
+    "prefix": ""
+  },
+  "aliases": {
+    "components": "@/components",
+    "utils": "@/lib/utils"
+  }
+}