Extract the AI provider/endpoints settings and the MCP server section out
of the Workspace "General" settings page into their own "AI" settings page,
reachable from a new sidebar entry.
- add page apps/client/.../settings/workspace/ai-settings.tsx (AiProviderSettings
admin-gated + McpSettings), with its own Helmet title
- register the /settings/ai route in App.tsx and add SETTINGS.WORKSPACE.AI
to app-route.ts
- add an "AI" item (IconSparkles) to the Workspace group in settings-sidebar
- trim workspace-settings.tsx back to the General section and drop the
now-unused imports
ea56985efd