Content: Automate Django Release Roadmap SVG and Add Template Safeguards for Missing Releases (#2297)

[rrrr08]

fixed #2297
This PR introduces the following improvements:

Automates the generation of the release roadmap SVG for the download page using a Python script and JSON data, similar to the Python devguide workflow.
Updates the download page template to reference the generated SVG, ensuring the roadmap stays up to date with each release cycle.
Adds template safeguards to prevent errors when the "current" release or its version is missing from the database, displaying a helpful message instead of breaking the page.
Protects all download links and release notes rendering from missing or incomplete release data, improving robustness for both development and production environments.

[pauloxnet]

fixed #2297 This PR introduces the following improvements:

Automates the generation of the release roadmap SVG for the download page using a Python script and JSON data, similar to the Python devguide workflow. Updates the download page template to reference the generated SVG, ensuring the roadmap stays up to date with each release cycle. Adds template safeguards to prevent errors when the "current" release or its version is missing from the database, displaying a helpful message instead of breaking the page. Protects all download links and release notes rendering from missing or incomplete release data, improving robustness for both development and production environments.

@rrrr08 thanks for working on this PR

In the issue #2297, I suggested imitating the automatic graph generation process as done in Python's devguide, but not copying also its graphics.

Could you preserve the graphics of the current graph but make it command-generated?

[rrrr08]

Yes sir I will preserve the graphics of the graph and make it command-generated. Thank you for the feedback.