Feat/ssad 0099/azure blobe storage

[Sohatzk]

Added azure blob storage
Moved Encryption/Decryption logic to a separate shared service
Added blob existence validation logic
Added unit tests for new logic
#99

[DrFaust555]

1. Problem: missing else/continue in ~7 handlers
   Repeats in GetAllAudiosHandler, GetAllImagesHandler, GetImageByStreetcodeIdHandler, GetStreetcodeArtByStreetcodeIdHandler, GetAllCategoriesHandler, GetCategoriesByStreetcodeIdHandler, GetArtsByStreetcodeIdHandler:

var audioBase64 = await _blobService.FindFileInStorageAsBase64(audio.BlobName);
if (audioBase64 is not null)
{
audio.Base64 = audioBase64;
}
// BUG: this code is ALWAYS executed — even when the blob is found!
var errorNotFoundMsg = Messages.Error_MediaBlobNotFound.Format(...);
_logger.LogError(request, errorNotFoundMsg);
return Result.Fail(new Error(errorNotFoundMsg));
There is no else or continue after if — the handler always returns Fail, even when the blob is found successfully. GetAllNewsHandler and SortedByDateTimeHandler have the correct continue — this is a copy-paste error where continue was forgotten to be added in the rest.

Other inaccuracies:

2. Program.cs hardcodes AzureBlobService in RecurringJob:
   RecurringJob.AddOrUpdate(...)
   In Local environment AzureBlobService is not registered — will fail. IBlobService is required.
3. AzureBlobService.FindFileInStorageAsBytes returns null! — null-forgiving operator hides potential NullReferenceException. Return type should be Task<byte[]?>.
4. BlobService.SaveFileInStorageBase64 is broken — the result of FileService.EncryptFile() is discarded, unencrypted bytes are written to disk.
5. UpdateNewsHandler — Delete(newsEntity.Image) without null-check — if newsEntity.Image is also null, there will be a NullReferenceException.
6. AzureBlobService uses Console.WriteLine instead of ILogger for logging.
7. CleanBlobStorage loads ALL images and audios into memory via GetAllAsync() — a problem with large data.

Design issues
8. 0% tests on AzureBlobService and FileService — new 200+ lines of production code without coverage.
9. 9.9% duplication — blob-not-found pattern copy-pasted in 20 handlers. Should be moved to helper.

[sonarqubecloud]

Quality Gate failed

Failed conditions
67.8% Coverage on New Code (required ≥ 80%)
5.9% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud