This commit adds comprehensive support for ADLS Gen2 storage with multiple
authentication methods, full read/write capabilities, and local testing support
via Azurite emulator.

Backend changes:
- Add azure_sas_token field to cloud storage schemas and database models
- Implement ADLS storage options for access_key, service_principal, and sas_token auth
- Add ADLS path parsing utilities (az:// and abfs:// URI formats)
- Add Azure Blob Storage client integration with file listing capabilities
- Update cloud storage reader to support ADLS paths alongside S3
- Store and retrieve ADLS secrets (account_key, client_secret, sas_token)

Worker changes:
- Add ADLS storage options to worker models with secret decryption
- Enable ADLS write operations for all file formats (Parquet, CSV, JSON, Delta)
- Support all ADLS authentication methods in worker context

Frontend changes:
- Enable ADLS storage type option in cloud connection UI
- Add UI fields for Azure-specific credentials (account name, keys, tenant, etc.)
- Add SAS token authentication support with password field visibility toggle
- Add azure_sas_token to TypeScript type definitions and API conversions
- Update form validation for ADLS connection requirements

Dependencies:
- Add azure-storage-blob ^12.24.0 for Blob Storage SDK
- Add azure-identity ^1.19.0 for service principal authentication
- Add adlfs ^2025.1.0 for Polars integration

Testing infrastructure:
- Create test_utils/adls module for Azurite-based testing
- Add start_azurite and stop_azurite CLI commands
- Implement test data generator with Parquet, CSV, and JSON samples
- Add comprehensive README with usage examples and troubleshooting
- Create managed_azurite context manager for integration tests

Supported features:
- Multiple authentication methods: access key, service principal, SAS token
- Read operations: single files and directory wildcards
- Write operations: Parquet, CSV, JSON, Delta Lake formats
- Path formats: both az:// and abfs:// URI schemes
- Local testing with Azurite emulator (Docker-based)
- Secure secret storage with per-user encryption

Files modified: 9 backend/frontend files
Files created: 5 test utility files