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.

server/middleware/01.csrf.js

@@ -0,0 +1,46 @@
+import crypto from 'crypto'
+
+const SAFE_METHODS = new Set(['GET', 'HEAD', 'OPTIONS'])
+
+// Routes exempt from CSRF (external webhooks, magic link verify)
+const EXEMPT_PREFIXES = [
+  '/api/helcim/webhook',
+  '/api/slack/webhook',
+  '/api/auth/verify',
+]
+
+function isExempt(path) {
+  return EXEMPT_PREFIXES.some(prefix => path.startsWith(prefix))
+}
+
+export default defineEventHandler((event) => {
+  const method = getMethod(event)
+  const path = getRequestURL(event).pathname
+
+  // Always set a CSRF token cookie if one doesn't exist
+  let csrfToken = getCookie(event, 'csrf-token')
+  if (!csrfToken) {
+    csrfToken = crypto.randomBytes(32).toString('hex')
+    setCookie(event, 'csrf-token', csrfToken, {
+      httpOnly: false, // Must be readable by JS to include in requests
+      secure: process.env.NODE_ENV === 'production',
+      sameSite: 'lax',
+      path: '/'
+    })
+  }
+
+  // Only check state-changing methods
+  if (SAFE_METHODS.has(method)) return
+  if (!path.startsWith('/api/')) return
+  if (isExempt(path)) return
+
+  // Double-submit cookie check: header must match cookie
+  const headerToken = getHeader(event, 'x-csrf-token')
+
+  if (!headerToken || headerToken !== csrfToken) {
+    throw createError({
+      statusCode: 403,
+      statusMessage: 'CSRF token missing or invalid'
+    })
+  }
+})