ui: portable framework under app/a0ui

[3clyp50]

This PR reshapes the launcher around a clearer Docker-focused architecture and removes legacy naming from the previous service-version implementation.

What changed

• Renamed the feature from service_versions / service-versions to docker_manager / docker-manager across app and shell.
• Split the Docker UI into section-based components under app/components/docker-manager/ with co-located HTML and JS.
• Added a dedicated shared store for the Docker manager (docker-manager-store.js) and kept a thin app orchestrator (app/docker_manager.js).
• Moved low-level Docker code to shell/docker_adapter/ and feature orchestration to shell/docker_manager/ for clearer responsibility boundaries.
• Updated preload and IPC channel namespace to docker-manager:* with matching frontend API usage.
• Added volume management support in the flow (inventory/list/remove/prune) and Docker install trigger path for onboarding.
• Removed old test modal scaffolding and legacy launcher/service-version files no longer used.
• Updated and expanded docs (docs/) and created a comprehensive handoff update in AGENTS.md.

Notes

• This is a new implementation path, so no backward compatibility aliases were kept.
• The staged set also includes A0 UI core path/style updates and docs refresh to match the new architecture.