Integrate Azure Blob Storage for backend storage

[KillianLarcher]

Context

Portabase supports multiple storage providers (S3-compatible like AWS S3 or Cloudflare R2, Google Drive) used to store backups.

Objective

Add support for Azure Blob Storage as a new storage provider.

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Technical Implementation

1. Create Azure Blob Storage provider

Implement ping, get, upload, delete functions in:
src/features/storages/providers/azure-blob-storage.ts

2. Register provider in storage system

• Add azure-blob-storage option to provider handlers:
  src/features/storages/providers/index.ts

• Extend provider type system by adding azure-blob-storage to StorageProviderKind:
  src/features/storages/types.ts

3. Implement Azure Blob Storage configuration form (schema + UI)

• Create validation schema:
  src/components/wrappers/dashboard/admin/channels/channel/channel-form/providers/storages/forms/azure-blob-storage.schema.ts

• Create UI form component:
  src/components/wrappers/dashboard/admin/channels/channel/channel-form/providers/storages/forms/azure-blob-storage.form.tsx

4. Integrate Azure Blob Storage into UI provider system

• Update channel form schema:
  src/components/wrappers/dashboard/admin/channels/channel/channel-form/channel-form.schema.ts

• Update provider registry:
  src/components/wrappers/dashboard/admin/channels/helpers/storage.tsx
  Remove preview: true for Azure Blob Storage provider.

• Update form renderer:
  Add azure-blob-storage case in renderChannelForm in:
  src/components/wrappers/dashboard/admin/channels/helpers/common.tsx

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Validation Requirements (mandatory)

The Pull Request must include screenshots demonstrating:

• “Add Storage Channel” dialog showing Azure Blob Storage as an available provider
• Azure Blob Storage configuration form in create mode
• Azure Blob Storage configuration form in edit mode

First Good issue

This issue is suitable for first-time contributors familiar with TypeScript and React.