feat(web): move Cascade Defaults to Global section in sidebar

[aaight]

Summary

Move "Cascade Defaults" from Settings > General to the Global section of the dashboard sidebar, improving information architecture for platform-level configuration.

Changes

• New route: Created /web/src/routes/global/defaults.tsx — New page component for Global Defaults
• Route registration: Updated route-tree.ts to register the new route
• Sidebar navigation: Added "Cascade Defaults" entry to the Global nav section (superadmin-only visibility)
• Cleanup: Removed the Cascade Defaults section from Settings > General — now only contains Organization form

Architecture

The new Global Defaults page follows the existing global page pattern:

• Simple functional component wrapping the existing <DefaultsForm />
• Descriptive heading and subheading
• No new API endpoints or business logic — reuses existing tRPC endpoints
• Superadmin-only visibility (inherited from Global sidebar section wrapper)

Testing

• ✅ Type checking passes (zero TypeScript errors)
• ✅ All 4615 tests pass
• ✅ Linting passes (zero issues)
• ✅ Manual verification: New route file created, imports correct, route tree updated, sidebar navigation updated, cleanup completed

Notes

• No backend/tRPC changes required — this is pure frontend routing reorganization
• Users with superadmin role will see "Cascade Defaults" in the Global section of the sidebar
• Non-superadmin users who previously had access to defaults through Settings > General will now only see Organization settings there

https://trello.com/c/69b445174218dab444da6b14

[nhopeatall]

LGTM — Clean routing reorganization that follows existing global page patterns exactly.

The new defaults.tsx mirrors the structure of other global routes (self-contained component, createRoute with rootRoute, named export). The DefaultsForm is fully self-contained (fetches its own data via tRPC), so it works identically in the new location. Cleanup of Settings > General is complete with no stale imports or references. All CI checks pass.

One minor note (not blocking): The tRPC defaults router uses protectedProcedure (any authenticated user), not superAdminProcedure. Previously, admin/member users could access Cascade Defaults via Settings > General. Now the sidebar entry is only visible to superadmin users, but any authenticated user who navigates directly to /global/defaults can still view and modify defaults. This is consistent with how all other global routes work (no route-level guards, relying on sidebar visibility + backend auth), but the PR description's note about non-superadmin access is worth clarifying — they lose discoverability, not access.