feat: implement health statistics tracking (Phase 2.7 Task 2)

- Add HealthStatistics model with 10 stat types
- Implement HealthStatisticsRepository
- Create 6 health stats API endpoints
- Add trend analysis with summary calculations
- Follow medication repository pattern

Status: 60% complete, needs compilation fixes

test-meds.sh

@@ -0,0 +1,6 @@
+#!/bin/bash
+echo "Testing Medication API"
+curl -s http://solaria.solivarez.com.ar:8001/health
+echo ""
+echo "Registering user..."
+curl -s -X POST http://solaria.solivarez.com.ar:8001/api/auth/register -H "Content-Type: application/json" -d '{"email":"medtest@example.com","username":"medtest","password":"Password123!","first_name":"Test","last_name":"User"}'