Removes all module-related logic from the admin dashboard, CLI database
initialization, and AdminPages component:
- Drop `initModules` call from `db init` CLI command and simplify the
completion message to only reflect core feature tables
- Remove `getModuleDashboardStats` and module page routing from admin
stats actions and update usage documentation accordingly
- Simplify `AdminPagesClient` to remove module page loading, lazy
components, and module-specific props (`moduleStats`, `modulePageInfo`,
`routeInfo`, `enabledModules`)
