Fix #133: Add root route to fix 404 error on backend root URL

[hkc5]

Problem

When accessing the backend at 0.0.0.0:5001, users receive a 404 error. This is confusing because the server appears to start successfully but the root URL returns nothing.

Solution

Added a root route (/) that returns:

• Service name and status
• Available endpoints information
• API route prefixes

Changes

• Modified backend/app/__init__.py to add an @app.route('/') endpoint

Testing

The root endpoint now returns:

{
  "service": "MiroFish Backend",
  "status": "running",
  "version": "1.0.0",
  "endpoints": {
    "health": "/health",
    "api": {
      "graph": "/api/graph",
      "simulation": "/api/simulation",
      "report": "/api/report"
    }
  }
}

Fixes #133

[hkc5]

Hi @666ghj @hzr1937,

This PR fixes the 404 error when accessing the backend root URL (0.0.0.0:5001).

The issue was that Flask only had routes for /health and /api/*, causing confusion for users who expected to see something when accessing the backend directly.

Added a simple root route that returns service info and available endpoints.

Ready for review when you have time!

Thanks

[hkc5]

@hzr1937 @cursoragent @hzr1937