Add Bucket Policy, CORS, and Encryption config to Storage service

[NitinKumar004]

Summary

The Storage driver interface is missing bucket-level security and configuration operations that are essential for testing access control and compliance.

What's Missing

• Bucket Policy: PutBucketPolicy / GetBucketPolicy / DeleteBucketPolicy
• CORS Configuration: PutCORSConfig / GetCORSConfig / DeleteCORSConfig
• Encryption Configuration: PutBucketEncryption / GetBucketEncryption

Provider Mapping

Feature	AWS S3	Azure Blob	GCP GCS
Bucket Policy	BucketPolicy	Access Policy	IAM Policy on Bucket
CORS	CORS Configuration	CORS Rules	CORS Config
Encryption	ServerSideEncryption	Encryption Scope	Default Encryption

Why This Matters

• Security testing is blocked — can't verify that policies are correctly applied
• CORS is required for any frontend-to-storage integration test
• Encryption config is a compliance requirement in most organizations

Acceptance Criteria

• Add policy, CORS, and encryption methods to storage/driver/driver.go
• Implement in all 3 providers (S3, Blob Storage, GCS)
• Policy evaluation should support allow/deny logic
• Add tests covering all 3 providers