feat(storage-service): Update connection settings and remove unused sample commands

- Updated `appsettings.Development.json` to change the database connection string for the storage service.
- Added `Microsoft.EntityFrameworkCore.Design` package reference to the project file for design-time features.
- Removed obsolete command and handler files related to sample management, including `ChangeSampleStatusCommand`, `CreateSampleCommand`, `UpdateSampleCommand`, and their respective handlers.
- Cleaned up the `SamplesController` and related query and validation files to streamline the codebase.

services/storage-service-net/src/StorageService.API/appsettings.Development.json

@@ -8,7 +8,7 @@
     },
     "AllowedHosts": "*",
     "ConnectionStrings": {
-        "DefaultConnection": "Host=localhost;Port=5433;Database=storage_db;Username=postgres;Password=postgres"
+        "DefaultConnection": "Host=ep-holy-glitter-a4hongg7-pooler.us-east-1.aws.neon.tech;Port=5432;Database=storage_service;Username=neondb_owner;Password=npg_Ssfy6HKO0cXI;SSL Mode=Require"
     },
     "Storage": {
         "Provider": "minio",