Fix security and correctness issues found in full-codebase audit

- Restrict meetingPassword field so it isn't leaked via the public REST/GraphQL API
- Fix booking slot computation to use Europe/Berlin time instead of the server's UTC clock
- Reset email verification when a customer changes their email address
- Fix ICS calendar injection via unescaped carriage returns in event descriptions
- Bind WebRTC meeting kicks to a persistent client id so they survive a rejoin
- Move the meeting signaling token out of the WebSocket query string into the first message
- Prevent duplicate signaling connections from leaking when the same participant reconnects
- Use the rightmost X-Forwarded-For entry for rate limiting (single trusted reverse proxy)
- Use constant-time comparison for the cron endpoint's bearer token
- Remove SVG from allowed Media upload types (stored-XSS risk, unused anyway)
- Add baseline security headers and a CSP to next.config.ts
- Fix CI/CD script injection via unsanitized git ref names in release.yml

collections/Customers.ts

@@ -1,24 +1,40 @@
 import type { CollectionAfterChangeHook, CollectionBeforeChangeHook, CollectionConfig } from "payload";
-import { isAdminFieldLevel } from "@/access";
+import { isAdmin, isAdminFieldLevel } from "@/access";
 import { EMAIL_VERIFICATION_TTL_MS, generateVerificationToken, hashVerificationToken, verificationExpiryISO } from "@/lib/auth/verification";
 import { verificationEmail } from "@/lib/email/authTemplates";
 import { sendEmail } from "@/lib/email/sendBookingEmails";
 
-const isSelfOrAdmin = ({ req }: { req: { user?: { collection?: string; id?: unknown } | null } }) => {
-  const user = req.user;
+// Routes through the shared isAdmin check (role === "admin", not just
+// collection === "users") so this stays correct if a non-admin role is ever
+// added to Users — see the comment on isAdmin in access/index.ts.
+const isSelfOrAdmin: typeof isAdmin = (args) => {
+  const user = args.req.user;
   if (!user) return false;
-  if (user.collection === "users") return true;
+  if (user.collection === "users") return isAdmin(args);
   if (user.collection === "customers") return { id: { equals: user.id } };
   return false;
 };
 
-// Runs on every new customer account: issues a random, single-use,
-// time-limited email-verification token. Only its hash is ever persisted
-// (see the emailVerificationTokenHash field below) — the plaintext exists
-// only in req.context for the afterChange hook below to email out, and is
-// never written to the database or logged.
-const issueVerificationToken: CollectionBeforeChangeHook = ({ data, operation, req }) => {
-  if (operation !== "create") return data;
+// Runs on every new customer account, and again whenever an existing
+// customer changes their email address: issues a random, single-use,
+// time-limited email-verification token and resets emailVerified to false.
+// Only the token's hash is ever persisted (see emailVerificationTokenHash
+// below) — the plaintext exists only in req.context for the afterChange
+// hook below to email out, and is never written to the database or logged.
+//
+// The email-change case matters because `update` access on this collection
+// is isSelfOrAdmin and the auto-added `email` field carries no field-level
+// access of its own — without this, a customer could verify a throwaway
+// address once and then repoint `email` at an address they don't own while
+// keeping emailVerified: true (which gates booking-confirmation emails).
+const issueVerificationToken: CollectionBeforeChangeHook = ({ data, originalDoc, operation, req }) => {
+  const emailChanged =
+    operation === "update" &&
+    typeof data.email === "string" &&
+    typeof originalDoc?.email === "string" &&
+    data.email !== originalDoc.email;
+  if (operation !== "create" && !emailChanged) return data;
+
   const token = generateVerificationToken();
   data.emailVerified = false;
   data.emailVerificationTokenHash = hashVerificationToken(token);
@@ -27,8 +43,7 @@ const issueVerificationToken: CollectionBeforeChangeHook = ({ data, operation, r
   return data;
 };
 
-const sendVerificationEmail: CollectionAfterChangeHook = async ({ doc, operation, req }) => {
-  if (operation !== "create") return doc;
+const sendVerificationEmail: CollectionAfterChangeHook = async ({ doc, req }) => {
   const token = req.context.pendingVerificationToken;
   if (typeof token !== "string") return doc;
   try {
@@ -69,7 +84,7 @@ export const Customers: CollectionConfig = {
     create: () => true,
     read: isSelfOrAdmin,
     update: isSelfOrAdmin,
-    delete: ({ req }) => req.user?.collection === "users",
+    delete: isAdmin,
   },
   hooks: {
     beforeChange: [issueVerificationToken],