feat(storage): refactor storage config and remove module registry

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.

src/shared/lib/appConfig.js

@@ -3,8 +3,6 @@
  * Centralized configuration management for the entire package
  */
 
-import { getAvailableModules } from '../../modules/modules.registry.js';
-
 /**
  * Get application name from environment variables
  * @returns {string} Application name
@@ -36,28 +34,6 @@ export function getPublicBaseUrl() {
   return String(raw).replace(/\/$/, '');
 }
 
-/**
- * Get enabled modules configuration (server-side only)
- * This function dynamically reads from modules.registry.js and checks environment variables
- * Use this on the server and pass the result to client components as props
- * 
- * To enable a module, set the environment variable: ZEN_MODULE_{NAME}=true
- * Example: ZEN_MODULE_INVOICE=true
- * 
- * @returns {Object} Object with module names as keys and boolean values
- */
-export function getModulesConfig() {
-  const modules = {};
-  const availableModules = getAvailableModules();
-  
-  for (const moduleName of availableModules) {
-    const envVar = `ZEN_MODULE_${moduleName.toUpperCase()}`;
-    modules[moduleName] = process.env[envVar] === 'true';
-  }
-  
-  return modules;
-}
-
 /**
  * Get application configuration
  * @returns {Object} Application configuration object
@@ -68,10 +44,7 @@ export function getAppConfig() {
     sessionCookieName: getSessionCookieName(),
     timezone: process.env.ZEN_TIMEZONE || 'America/Toronto',
     dateFormat: process.env.ZEN_DATE_FORMAT || 'YYYY-MM-DD',
-    // Currency configuration (for currency module)
     defaultCurrency: process.env.ZEN_CURRENCY || 'CAD',
     currencySymbol: process.env.ZEN_CURRENCY_SYMBOL || '$',
-    // Enabled modules
-    modules: getModulesConfig(),
   };
 }