[Enhancement]: Add Azure Managed Identity (MI) Support for Blob Storage Authentication #10784

What features would you like to see added?

I would like LibreChat to support Azure Managed Identity (MI) authentication for Azure Blob Storage. Specifically, LibreChat should be able to authenticate to Azure Blob Storage without requiring a connection string or account key, by leveraging:

• DefaultAzureCredential
• ManagedIdentityCredential
• Pod-assigned or user-assigned managed identities on AKS

This enables secure, keyless, identity-based access to storage using Azure AD, fully aligned with cloud-native best practices.

More details

Currently, LibreChat supports Azure Blob Storage only via:

• AZURE_STORAGE_CONNECTION_STRING
• Account name + account key (AZURE_STORAGE_ACCOUNT_NAME, AZURE_STORAGE_ACCESS_KEY)
• (Partial) SAS tokens

However, LibreChat does not support Azure AD / Managed Identity authentication.

For AKS and other Azure environments, using connection strings or storage keys is discouraged because:

• Keys cannot be scoped per service
• Keys cannot be revoked per identity
• Rotation is difficult
• Connection strings give full storage account access
• Managed Identity provides least-privilege, identity-based access without secrets

Azure Blob Storage supports MI authentication via the official Azure SDK:

import { DefaultAzureCredential } from "@azure/identity";
const credential = new DefaultAzureCredential();
const client = new BlobServiceClient(
  `https://${account}.blob.core.windows.net`,
  credential
);

### Which components are impacted by your request?

_No response_

### Pictures

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### Code of Conduct

- [x] I agree to follow this project's Code of Conduct