Reorganize docs/user-manual/ from flat structure to language subdirectories
(zh/, en/, ja/) with shared assets/. Move existing Chinese docs into zh/,
fix image paths, add multilingual navigation README, and translate all 23
markdown files (~4500 lines each) to English and Japanese.
- Update version numbers in package.json, Cargo.toml, tauri.conf.json
- Add CHANGELOG.md entry for v3.11.0
- Add trilingual release notes (zh/en/ja)
- Update user manual version info