OpenConceptLab/ocl_online#58 | Add user usage dashboard route and homepage widget

- Add SelfOrStaffRoute wrapper for routes accessible to the user or staff
- Add /users/:user/usage route rendering UsageDashboard for non-staff users
- Add compact "Your Activity This Month" widget to homepage dashboard sidebar
  Shows total API requests, top operation, and link to full dashboard
- Install @mui/x-charts as dependency (peer dep for ocl-analytics-web)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: paynejd