- add `ZEN_DEVKIT` env variable to enable/disable devkit
- add `isDevkitEnabled()` utility and export it from public api
- register devkit nav section and items conditionally when devkit is enabled
- add devkit route handling in admin page client and server
- add DevkitPage, ComponentsPage, and IconsPage client components
Introduce a dedicated `storage-config.js` for registering public
prefixes and access policies via `configureStorageApi()`, replacing the
previous `getAllStoragePublicPrefixes` / `getAllStorageAccessPolicies`
imports from the module registry.
Remove `getAllApiRoutes()` from the router so module-level routes are no
longer auto-collected; feature routes must now be registered explicitly
via `registerFeatureRoutes()` during `initializeZen()`.
Update `.env.example` to document separate `ZEN_STORAGE_PROVIDER`,
`ZEN_STORAGE_B2_*` variables for Backblaze B2 alongside the existing
Cloudflare R2 variables, making provider selection explicit.
Clean up admin navigation and page components to drop module-injected
nav entries, keeping only core and system sections.
hykocx