refactor!: replace Zustand global store with TanStack Query for systemFeatures

Follow-up to SSR prefetch migration (2833965). Eliminates the Zustand
middleman that was syncing TanStack Query data into a separate store.

- Remove useGlobalPublicStore Zustand store entirely
- Create hooks/use-global-public.ts with useSystemFeatures,
  useSystemFeaturesQuery, useIsSystemFeaturesPending, useSetupStatusQuery
- Migrate all 93 consumers to import from @/hooks/use-global-public
- Simplify global-public-context.tsx to a thin provider component
- Update 18 test files to mock the new hook interface
- Fix SetupStatusResponse.setup_at type from Date to string (JSON)
- Fix setup-status.spec.ts mock target to match consoleClient

BREAKING CHANGE: useGlobalPublicStore is removed. Use useSystemFeatures()
from @/hooks/use-global-public instead.

web/app/components/plugins/plugin-page/context.spec.tsx

@@ -1,7 +1,7 @@
 import { render, screen } from '@testing-library/react'
 import { beforeEach, describe, expect, it, vi } from 'vitest'
 // Import mocks
-import { useGlobalPublicStore } from '@/context/global-public-context'
+import { useSystemFeatures } from '@/hooks/use-global-public'
 
 import { PluginPageContext, PluginPageContextProvider, usePluginPageContext } from './context'
 
@@ -11,7 +11,7 @@ vi.mock('nuqs', () => ({
 }))
 
 vi.mock('@/context/global-public-context', () => ({
-  useGlobalPublicStore: vi.fn(),
+  useSystemFeatures: vi.fn(),
 }))
 
 vi.mock('../hooks', () => ({
@@ -25,12 +25,11 @@ vi.mock('../hooks', () => ({
   ],
 }))
 
-// Helper function to mock useGlobalPublicStore with marketplace setting
+// Helper function to mock useSystemFeatures with marketplace setting
 const mockGlobalPublicStore = (enableMarketplace: boolean) => {
-  vi.mocked(useGlobalPublicStore).mockImplementation((selector) => {
-    const state = { systemFeatures: { enable_marketplace: enableMarketplace } }
-    return selector(state as Parameters<typeof selector>[0])
-  })
+  vi.mocked(useSystemFeatures).mockReturnValue({
+    enable_marketplace: enableMarketplace,
+  } as ReturnType<typeof useSystemFeatures>)
 }
 
 // Test component that uses the context