Implement OWASP ASVS L1 security remediation (Phases 0-2)

Auth: Add requireAuth/requireAdmin guards with JWT cookie verification,
member status checks (suspended/cancelled = 403), and admin role
enforcement. Apply to all admin, upload, and payment endpoints. Add
role field to Member model.

CSRF: Double-submit cookie middleware with client plugin. Exempt
webhook and magic-link verify routes.

Headers: X-Content-Type-Options, X-Frame-Options, X-XSS-Protection,
Referrer-Policy, Permissions-Policy on all responses. HSTS and CSP
(Helcim/Cloudinary/Plausible sources) in production only.

Rate limiting: Auth 5/5min, payment 10/min, upload 10/min, general
100/min via rate-limiter-flexible, keyed by client IP.

XSS: DOMPurify sanitization on marked() output with tag/attr
allowlists. escapeHtml() utility for email template interpolation.

Anti-enumeration: Login returns identical response for existing and
non-existing emails. Remove 404 handling from login UI components.

Mass assignment: Remove helcimCustomerId from profile allowedFields.

Session: 7-day token expiry, refresh endpoint, httpOnly+secure cookies.

Environment: Validate required secrets on startup via server plugin.
Remove JWT_SECRET hardcoded fallback.

app/middleware/admin.js

@@ -1,18 +1,17 @@
-export default defineNuxtRouteMiddleware((to) => {
-  // Skip middleware in server-side rendering to avoid errors
-  if (process.server) return
-  
-  // TODO: Temporarily disabled for testing - enable when authentication is set up
-  // Check if user is authenticated (you'll need to implement proper auth state)
-  // const isAuthenticated = useCookie('auth-token').value
-  
-  // if (!isAuthenticated) {
-  //   throw createError({
-  //     statusCode: 401,
-  //     statusMessage: 'Authentication required'
-  //   })
-  // }
-  
-  // TODO: Add proper role-based authorization
-  // For now, we assume anyone with a valid token is an admin
-})
+export default defineNuxtRouteMiddleware(async (to) => {
+  if (import.meta.server) return
+
+  const { isAuthenticated, memberData, checkMemberStatus } = useAuth()
+
+  if (!isAuthenticated.value) {
+    await checkMemberStatus()
+  }
+
+  if (!isAuthenticated.value) {
+    return navigateTo('/')
+  }
+
+  if (memberData.value?.role !== 'admin') {
+    return navigateTo('/members')
+  }
+})