feat: add ribbon layer selector with layer actions and state restore

[mlightcad]

Summary

• Add a new MlLayerSelect component with searchable layer options, inline state toggles (on/frozen/locked), line preview, and localized tooltips.
• Expand ribbon Home tab layer tooling to support layer selection plus action buttons (off/isolate/freeze/lock/current/all-on/unisolate/thaw/unlock/restore).
• Refactor useLayers into a fuller layer state manager with document/sysvar sync, mutation helpers, and snapshot capture/restore.
• Align related UI surfaces (MlLayerDrawStyleToolbar, MlLayerList) to reuse useLayers operations instead of ad-hoc DB writes.
• Update layer icon assets and bump @mlightcad/ribbon from 0.0.8 to 0.0.9.

Why

• Provide AutoCAD-style layer workflows directly in the ribbon for faster drawing-state control.
• Centralize layer state mutation and synchronization logic to reduce duplicated behavior and improve consistency across components.
• Improve usability with richer tooltips, searchable layer selection, and one-click state actions.

What Changed

• packages/cad-viewer/src/component/common/MlLayerSelect.vue added as a reusable, interactive layer selector.
• packages/cad-viewer/src/composable/useLayers.ts now exposes:
  • layer state toggles (on, frozen, locked)
  • isolate/all-on actions
  • current-layer setter
  • snapshot capture/apply for restore behavior
  • document/sysvar event binding and cleanup
• packages/cad-viewer/src/component/layout/MlRibbonCommands.vue integrates useLayers and adds new ribbon layer action handling, including isolate snapshot + restore flow.
• packages/cad-viewer/src/component/layout/MlLayerDrawStyleToolbar.vue switches to MlLayerSelect and layer-state toggle events.
• packages/cad-viewer/src/component/palette/MlLayerList.vue now calls shared composable methods (setLayerOn, setLayerColor).
• packages/cad-viewer/src/locale/en/main.ts and packages/cad-viewer/src/locale/zh/main.ts add new ribbon/layer tooltip and selector strings.
• packages/cad-viewer/src/svg/layer/* adds isolate/light/locker/snow/unisolate icons and updates existing layer icons.
• packages/cad-viewer/package.json and pnpm-lock.yaml upgrade @mlightcad/ribbon to 0.0.9.

Risks / Notes

• LayerInfo shape changed (isHidden -> isFrozen), which may impact any downstream code that referenced the old property.
• MlLineWeightSelect moved from i18n labels to fixed English labels and excludes ByDIPs; confirm this is intended UX behavior.
• Layer restore/isolation state is in-memory per active session/document activation flow; validate expected behavior across document switches.