chore: reorganize life_tools structure and docs

[mcoder2014]

Summary

• reorganize source layout by application type: CLI tools under cli/, plugins under emby_plugins/, GUI apps under gui/
• move InterviewTimer from remote master into gui/interview_timer and update its workflow, docs, release notes, and ignore rules
• shorten README into an overview/catalog page and move detailed application docs under docs/cli/, docs/plugins/, and docs/gui/
• add detailed docs for each CLI tool, including design notes, code structure, core flows, and Mermaid diagrams

Validation

• git rebase origin/master
• git diff --check origin/master
• Mermaid syntax parse for 8 markdown code blocks with mermaid.parse
• ./build.sh
• go test ./cli/...
• PYTHONDONTWRITEBYTECODE=1 python3 -m py_compile cli/video_subtitle/video_subtitle.py cli/video_subtitle/video_subtitle_test.py cli/video_subtitle/lib/*.py
• PYTHONDONTWRITEBYTECODE=1 PYTHON=/private/tmp/life_tools_video_subtitle_venv/bin/python /private/tmp/life_tools_video_subtitle_venv/bin/python -m unittest cli/video_subtitle/video_subtitle_test.py
• cd gui/interview_timer && swift test
• cd gui/interview_timer && swift build --product InterviewTimerApp
• cd gui/interview_timer && ./scripts/build_app.sh

Not Run

• dotnet test emby_plugins/video_subtitle/LifeTools.Emby.VideoSubtitle.sln
• dotnet build emby_plugins/video_subtitle/LifeTools.Emby.VideoSubtitle.sln

dotnet is not installed in the local environment.