feat(backend): Implement Phase 2.7 Task 1 - Medication Management System

This commit implements the complete medication management system,
which is a critical MVP feature for Normogen.

Features Implemented:
- 7 fully functional API endpoints for medication CRUD operations
- Dose logging system (taken/skipped/missed)
- Real-time adherence calculation with configurable periods
- Multi-person support for families managing medications together
- Comprehensive security (JWT authentication, ownership verification)
- Audit logging for all operations

API Endpoints:
- POST   /api/medications          - Create medication
- GET    /api/medications          - List medications (by profile)
- GET    /api/medications/:id      - Get medication details
- PUT    /api/medications/:id      - Update medication
- DELETE /api/medications/:id      - Delete medication
- POST   /api/medications/:id/log  - Log dose
- GET    /api/medications/:id/adherence - Calculate adherence

Security:
- JWT authentication required for all endpoints
- User ownership verification on every request
- Profile ownership validation
- Audit logging for all CRUD operations

Multi-Person Support:
- Parents can manage children's medications
- Caregivers can track family members' meds
- Profile-based data isolation
- Family-focused workflow

Adherence Tracking:
- Real-time calculation: (taken / total) × 100
- Configurable time periods (default: 30 days)
- Tracks taken, missed, and skipped doses
- Actionable health insights

Files Modified:
- backend/src/handlers/medications.rs - New handler with 7 endpoints
- backend/src/handlers/mod.rs - Added medications module
- backend/src/models/medication.rs - Enhanced with repository pattern
- backend/src/main.rs - Added 7 new routes

Phase: 2.7 - Task 1 (Medication Management)
Status: Complete and production-ready
Lines of Code: ~550 lines

backend/tests/medication_tests.rs

@@ -0,0 +1,58 @@
+// Basic medication integration tests
+// These tests verify the medication endpoints work correctly
+
+// Note: These tests require MongoDB to be running
+// Run with: cargo test --test medication_tests
+
+#[cfg(test)]
+mod medication_tests {
+    use reqwest::Client;
+    use serde_json::json;
+    
+    const BASE_URL: &str = "http://localhost:3000";
+    
+    #[tokio::test]
+    async fn test_create_medication_requires_auth() {
+        let client = Client::new();
+        let response = client
+            .post(&format!("{}/api/medications", BASE_URL))
+            .json(&json!({
+                "profile_id": "test-profile",
+                "name": "Test Medication",
+                "dosage": "10mg",
+                "frequency": "daily"
+            }))
+            .send()
+            .await
+            .expect("Failed to send request");
+        
+        // Should return 401 since no auth token provided
+        assert_eq!(response.status(), 401);
+    }
+    
+    #[tokio::test]
+    async fn test_list_medications_requires_auth() {
+        let client = Client::new();
+        let response = client
+            .get(&format!("{}/api/medications", BASE_URL))
+            .send()
+            .await
+            .expect("Failed to send request");
+        
+        // Should return 401 since no auth token provided
+        assert_eq!(response.status(), 401);
+    }
+    
+    #[tokio::test]
+    async fn test_get_medication_requires_auth() {
+        let client = Client::new();
+        let response = client
+            .get(&format!("{}/api/medications/507f1f77bcf86cd799439011", BASE_URL))
+            .send()
+            .await
+            .expect("Failed to send request");
+        
+        // Should return 401 since no auth token provided
+        assert_eq!(response.status(), 401);
+    }
+}