Add basic backend infrastructure

Signed-off-by: Felipe Cardoso <felipe.cardoso@hotmail.it>

backend/app/services/sample_manager.py

@@ -0,0 +1,15 @@
+from typing import List
+
+from app.models.sample import Sample
+
+
+class SampleManager:
+    async def list_samples(self, limit: int, offset: int) -> List[Sample]:
+        # Implementation for listing samples from SFTP
+        # This is a placeholder - actual implementation needed
+        pass
+
+    async def get_latest_samples(self, count: int) -> List[Sample]:
+        # Implementation for getting latest samples
+        # This is a placeholder - actual implementation needed
+        pass