feat: automatic generation of release notes

[dawidgora]

Add GitHub-style automatic release notes generation

• Add server-side release notes generator that discovers the base tag, gathers merged PRs and contributors, and returns formatted Markdown plus the selected previous tag for reuse.
• Expose a /releases/generate-notes endpoint with form validation, localization strings, and UI wiring (button, previous-tag dropdown, JS handler) on the new release page to trigger note generation.
• Cover the generator with unit tests for default and tag-fallback flows.

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Screenshots

[wxiaoguang]

Also cc @techknowlogick for further review and help (#35976 (comment)) , in case you already have more discussions.

[dawidgora]

In 1406ccc:

• Added helpers so release notes pick the release immediately before the one being edited, not just the latest one
• This avoids errors when updating notes on older releases because we now compare against the correct predecessor tag.

[dawidgora]

In followup PR, when I find some time I will implement additional configuration for this feature, like it is on GitHub: https://docs.github.com/en/repositories/releasing-projects-on-github/automatically-generated-release-notes

[wxiaoguang]

Too many unnecessary if and ? for "defensive programming"
Most of them should be removed. If you write a if or ? , then you should clearly know that in which case it can happen.

Still many if and ? in code that I don't understand.

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And #35977 (comment)

Also cc techknowlogick for further review and help (#35976 (comment)) , in case you already have more discussions.

[dawidgora]

Too many unnecessary if and ? for "defensive programming"
Most of them should be removed. If you write a if or ? , then you should clearly know that in which case it can happen.

Still many if and ? in code that I don't understand.

Ok, I made it less defensive now @wxiaoguang

And #35977 (comment)

Also cc techknowlogick for further review and help (#35976 (comment)) , in case you already have more discussions.

We haven't, but @techknowlogick feel free to review my PR

[wxiaoguang]

TBH, still questions (only a quick look, not carefully look into backend code yet)