Add AI-powered nutrition and plan modules

Introduces DSPy-based nutrition and plan generation modules, including image analysis for nutritional info and personalized diet/exercise plans. Adds new API endpoints for health metrics/goals, nutrition image analysis, and plan management. Updates models, schemas, and backend structure to support these features, and includes initial training data and configuration for prompt optimization.

frontend/src/pages/Dashboard.jsx

@@ -13,6 +13,10 @@ const Dashboard = () => {
                     <h2 className="text-2xl font-bold mb-2">Health Metrics</h2>
                     <p className="text-gray-400">Track weight and blood indicators.</p>
                 </Link>
+                <Link to="/plans" className="p-6 bg-gray-800 rounded-lg shadow-lg hover:bg-gray-700 transition">
+                    <h2 className="text-2xl font-bold mb-2">AI Coach</h2>
+                    <p className="text-gray-400">Get personalized diet & workout plans.</p>
+                </Link>
             </div>
         </div>
     );