refactor(workflow): add Jinja2 renderer abstraction for template transform

[laipz8200]

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Summary

• Part of Minimal DI for workflow nodes via node_factory constructor injection #30506
• Introduce a Jinja2 template renderer abstraction for TemplateTransform with a CodeExecutor-backed adapter.
• Inject the renderer via TemplateTransformNode and DifyNodeFactory while keeping default behavior intact.
• Update TemplateTransform unit tests to mock the renderer output.
• Tests: make lint, make type-check.

Screenshots

Before	After
N/A	N/A

Checklist

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[gemini-code-assist]

Summary of Changes

Hello @laipz8200, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the TemplateTransformNode to utilize dependency injection for its template rendering capabilities. The primary goal is to decouple the node from its CodeExecutor dependency, making the component more modular, easier to test, and aligned with modern software design principles. This change introduces a new template renderer abstraction and updates the node factory to manage and inject this dependency.

Highlights

• Dependency Injection for TemplateTransformNode: The TemplateTransformNode now supports constructor-based dependency injection for its template rendering logic, specifically for the CodeExecutor dependency.
• New Template Renderer Abstraction: A new Jinja2TemplateRenderer protocol and its concrete implementation, CodeExecutorJinja2TemplateRenderer, have been introduced to abstract the template rendering process.
• Node Factory Integration: The NodeFactory has been updated to instantiate and inject the CodeExecutorJinja2TemplateRenderer into TemplateTransformNode instances upon creation, ensuring proper dependency management.
• Improved Testability and Modularity: By introducing dependency injection, the TemplateTransformNode is now more modular and testable, as its rendering mechanism can be easily mocked or swapped.

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[gemini-code-assist]

Code Review

This pull request refactors the template transformation node by introducing a Jinja2TemplateRenderer protocol and its CodeExecutorJinja2TemplateRenderer implementation. This change abstracts the template rendering logic, allowing TemplateTransformNode and NodeFactory to use dependency injection for the renderer, thereby enhancing modularity and testability. The TemplateTransformNode now utilizes this new renderer, catching TemplateRenderError instead of CodeExecutionError, and its unit tests have been updated to reflect these architectural changes, including patching the new renderer's method and adjusting mock return values. A review comment suggests explicitly inheriting CodeExecutorJinja2TemplateRenderer from Jinja2TemplateRenderer for improved clarity and static type checking.