feat(azure): implement Phase 3 Azure Blob Storage core operations and multi-CSP routing

[skyoo2003]

Overview

Implements Phase 3 Azure Blob Storage pilot and multi-CSP protocol/routing engine according to docs/roadmap.md.

Key Changes

• OpenAPI Codegen Pipeline:
  • Expanded api/models/azure-blob-storage.json to full OpenAPI 3.0 specification covering 9 core container and BlockBlob operations with specific query constraints (?restype=container, ?comp=list).
  • Implemented internal/codegen/openapi_parser.go converting OpenAPI JSON into ir.Model, sorting routes by query constraint specificity for deterministic routing in httproute.Match.
  • Re-generated router, types, errors, and base provider under internal/generated/blob/.
• Multi-CSP Auth & Gateway Protocol Detection:
  • Activated "azure" in internal/config/config.go.
  • Added support in internal/auth/azure_shared_key.go for SharedKey, SharedKeyLite, SAS query parameters, and local emulator path format (/devstoreaccount1).
  • Updated internal/gateway/protocol.go with isAzureRequest protocol sniffing to route Azure requests to ("rest-xml", "blob").
  • Added Azure-compliant XML error serialization (<Error><Code>...</Code><Message>...</Message></Error>) and x-ms-error-code header handling in internal/gateway/router.go.
• Native Azure Blob Storage Provider & Local Storage Engine:
  • Implemented thread-safe FileStore in internal/services/blob/store.go storing container data and metadata with path traversal guards.
  • Implemented internal/services/blob/provider.go handling container & BlockBlob operations, standard Azure response headers, Range requests (HTTP 206, Content-Range), and XML EnumerationResults listing.
• Testing & Verification:
  • Added unit test suites for openapi_parser, azure_shared_key, and blob provider/store.
  • Added end-to-end compatibility tests in test/compatibility/test_azure_blob.py with azure-storage-blob Python SDK.
  • Updated docs/coverage.md, docs/services/azure.md, and docs/architecture.md.

Verification

• make test: All Go unit and integration tests passing.
• pytest test/compatibility/test_azure_blob.py: Compatibility tests against live binary passing.