feat: add ratatui TUI dashboard and compose file auto-discovery

- TUI dashboard with 3 tabs: Services (table + detail bar), Events
  (scrollable timeline), Logs (per-service viewer) — polls StateStore
  every 500ms for real-time updates
- Color-coded service phases and event types, keybindings (q/Tab/j/k/g/G/?)
- New `vz stack dashboard <name>` command for attaching to running stacks
- Integrated into `vz stack up` foreground mode (--no-tui to disable)
- Auto-discover compose files: tries compose.yaml, compose.yml,
  docker-compose.yml, docker-compose.yaml in order (matching Docker
  Compose behavior)
- 118 CLI tests pass (19 new: 15 TUI unit + 3 CLI parse + 1 existing)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: lightsofapollo