feat: remove unused x-cal-timezone header and middleware matcher (#22398)

* feat: remove unused x-cal-timezone header and middleware matcher

- Remove x-cal-timezone header setting from middleware.ts
- Remove x-cal-timezone header setting from createNextApiHandler.ts
- Remove /api/trpc/:path* from middleware matcher
- Eliminates ~50M edge requests per month for unused functionality
- All timezone handling uses browser detection and localStorage instead

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

* update POST_METHODS_ALLOWED_API_ROUTES

* test: remove api/trpc POST validation test

- Remove test for /api/trpc/book/event POST requests since /api/trpc/:path* was removed from middleware matcher
- Keep test for /api/auth/signup which is still processed by middleware

Co-Authored-By: keith@cal.com <keithwillcode@gmail.com>

---------

Co-authored-by: Devin AI <158243242+devin-ai-integration[bot]@users.noreply.github.com>
Co-authored-by: hbjORbj <sldisek783@gmail.com>

packages/trpc/server/createNextApiHandler.ts

@@ -1,5 +1,3 @@
-import { z } from "zod";
-
 import type { AnyRouter } from "@trpc/server";
 import { createNextApiHandler as _createNextApiHandler } from "@trpc/server/adapters/next";
 
@@ -43,9 +41,6 @@ export function createNextApiHandler(router: AnyRouter, isPublic = false, namesp
         headers: {},
       };
 
-      const timezone = z.string().safeParse(ctx.req?.headers["x-vercel-ip-timezone"]);
-      if (timezone.success) defaultHeaders.headers["x-cal-timezone"] = timezone.data;
-
       // We need all these conditions to be true to set cache headers
       if (!(isPublic && allOk && isQuery)) return defaultHeaders;