Synchronize the fixes from #1936, #1824, and #1961 across translated editions and normalize C# and Dart formatting. Move Java CI to Ubuntu 24.04 so its Java 11/17 checks can run.
Use repository-relative image paths in the five language READMEs and add descriptive language badge alt text. Point the Russian README header to the existing shared image.
Replace the exercise pages' Python-only snippets with source-backed implementations for the 13 visible programming languages, and localize reader-facing comments by site language. Zig remains out of scope.
Approval bypass: repository protection requires one approval but does not enforce it for administrators. All 68 completed checks succeeded; four non-required Java jobs remained queued on the existing ubuntu-20.04 workflow, with no failed checks.
Add dedicated chapter exercise sections and generated exercise pages for the English, Japanese, and Russian editions.
Add navigation for all published languages while keeping Taiwan Traditional Chinese exercise pages generated at build time.
* Update the contributors list.
* Update the version number.
* Sync zh and zh-hant versions.
* Move epub builder to the utils branch.
* Optimize all figure files using pngquant.
* Update copyright.
* Update Acknowledgements.
* Update buttons in README.
* docs: add Japanese documents (`ja/docs`)
* docs: add Japanese documents (`ja/codes`)
* docs: add Japanese documents
* Remove pythontutor blocks in ja/
* Add an empty at the end of each markdown file.
* Add the missing figures (use the English version temporarily).
* Add index.md for Japanese version.
* Add index.html for Japanese version.
* Add missing index.assets
* Fix backtracking_algorithm.md for Japanese version.
* Add avatar_eltociear.jpg. Fix image links on the Japanese landing page.
* Add the Japanese banner.
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Co-authored-by: krahets <krahets@163.com>
