[Issue#2] Add subcomponents detection and dashboard integration

[storchk]

Github issue: #2

This PR introduces a Subcomponents tab on the Component Detail page, allowing users to discover and navigate component families (e.g., Button.Primary, Button.Secondary). It also surfaces the total family usage in the component info panel.

Changes

• Backend
  • New API endpoint: GET /workspaces/:workspaceSlug/components/:definitionId/subcomponents
  • New service getComponentSubcomponents that finds components matching ^Name\. in the same package and aggregates their usage
  • Computes familyUsage as the sum of the root component's usages plus all subcomponent usages
• Frontend
  • Added SubcomponentsTable with loading skeletons, empty state, and links to subcomponent detail pages
  • Integrated tab into ComponentDetail with subcomponent counter
  • Updated ComponentDetailInfo to display # Root used
• Docs
  • Added docs/dashboard/components/subcomponents.md
  • Updated Components overview and navigation links

Component details

Component overview

How to test

1. Open any component detail page that has subcomponents (e.g., Button)
2. Verify the Subcomponents tab appears between Props and Dependency tree
3. Confirm the table lists subcomponent names and usage counts
4. Confirm the left panel shows # Root used