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.

backend/app/db.py

@@ -1,12 +1,15 @@
-from sqlmodel import SQLModel, create_engine, Session, text
+from sqlmodel import Session, SQLModel, create_engine, text
+
 from app.config import settings
 
 engine = create_engine(settings.DATABASE_URL)
 
+
 def get_session():
     with Session(engine) as session:
         yield session
 
+
 def init_db():
     with Session(engine) as session:
         session.exec(text("CREATE EXTENSION IF NOT EXISTS vector"))