Add LangChainAzureHook for Azure OpenAI support

[ColtenOuO]

Summary

LangChainHook's docstring already flagged this gap: "Providers with bespoke auth (AWS Bedrock, Google Vertex AI / GenAI, Azure OpenAI, Cohere, HuggingFace) reject these kwargs; per-vendor subclasses can be added later mirroring the pydantic-ai pattern." PydanticAIHook already has that pattern (PydanticAIAzureHook/PydanticAIBedrockHook/PydanticAIVertexHook, each overriding _get_provider_kwargs) -- this PR adds the first LangChain equivalent.

Without it, LangChainHook always calls init_chat_model(model, api_key=..., base_url=...), but Azure OpenAI's LangChain classes (AzureChatOpenAI, AzureOpenAIEmbeddings) don't accept base_url -- they need azure_endpoint and api_version. Verified against the real langchain-openai package: those are the actual constructor fields/aliases.

Changes

• LangChainHook._connection_kwargs: @staticmethod -> instance method, so subclasses can override it (matches PydanticAIHook's _get_provider_kwargs). No behavior change for the base class.
• Add LangChainAzureHook(LangChainHook), overriding _connection_kwargs to map conn.host -> azure_endpoint and read api_version from conn.extra.
• Register the new langchain-azure connection type in provider.yaml; regenerated get_provider_info.py via breeze release-management prepare-provider-documentation --reapply-templates-only --skip-changelog --skip-readme (not hand-edited).

Test plan

• Added 7 tests: class attributes, UI field behaviour, host -> azure_endpoint mapping, api_version from extra, embedding model uses the same mapping, empty kwargs when no credentials set.
• Full test_langchain.py passes (28 passed).
• ruff format/ruff check, breeze run mypy clean (mypy caught the staticmethod/instance-method override incompatibility, since fixed).
• scripts/ci/prek/check_provider_yaml_files.py passes: LangChainAzureHook registered correctly, 0 errors.

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Was generative AI tooling used to co-author this PR?

• Yes — Claude Code (Sonnet 5)

[ColtenOuO]

Happy to add the remaining vendors (ex. Bedrock, Vertex) as follow-up PRs if that's a direction the maintainers would like to take.