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

app/(payload)/api/cron/event-reminders/route.ts

@@ -1,8 +1,16 @@
+import { timingSafeEqual } from "node:crypto";
 import { NextResponse } from "next/server";
 import { runEventReminders } from "@/lib/meeting/reminders";
 
 export const dynamic = "force-dynamic";
 
+function safeEqual(a: string, b: string): boolean {
+  const bufA = Buffer.from(a);
+  const bufB = Buffer.from(b);
+  if (bufA.length !== bufB.length) return false;
+  return timingSafeEqual(bufA, bufB);
+}
+
 /**
  * Intended to be called by an external cron job every few minutes, e.g.:
  *   curl -H "Authorization: Bearer $CRON_SECRET" https://anouma.org/api/cron/event-reminders
@@ -14,7 +22,7 @@ export async function GET(request: Request) {
   }
 
   const authHeader = request.headers.get("authorization");
-  if (authHeader !== `Bearer ${secret}`) {
+  if (!authHeader || !safeEqual(authHeader, `Bearer ${secret}`)) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
   }