test(e2e): send CSRF token on mutating requests and fix PAT UI selectors

The backend CSRF double-submit gate rejects unsafe methods unless
X-CSRF-Token mirrors the signed nz-csrf cookie. page.request bypasses the
SPA JS that does this, so every mutating E2E call got 403, failing the suite.

- Add csrfHeaders(page) helper that mirrors the nz-csrf cookie into the
  header, polling until the cookie is readable to avoid the post-login race.
- Apply it to all cookie-authenticated POST/PATCH/DELETE calls (the /mcp
  Bearer calls stay header-free since PAT requests are CSRF-exempt).
- loginAs waits for the nz-csrf cookie before returning.
- Fix the create-token dialog submit selector: the button is labelled
  'Create API token' (t('CreateApiToken')), not 'Create'.

Verified 8/8 passing across repeated CI-mode runs against a real backend.

Co-authored-by: cloudcode <cloudcode@users.noreply.github.com>

tests/e2e/fm-csrf.spec.ts

@@ -1,6 +1,6 @@
 import { expect } from "@playwright/test"
 
-import { test } from "./fixtures"
+import { csrfHeaders, test } from "./fixtures"
 
 test("file manager creation only accepts POST", async ({ adminPage: page }) => {
     const getResp = await page.request.get("/api/v1/file?id=1", {
@@ -13,6 +13,7 @@ test("file manager creation only accepts POST", async ({ adminPage: page }) => {
 
     const postResp = await page.request.post("/api/v1/file?id=1", {
         failOnStatusCode: false,
+        headers: await csrfHeaders(page),
     })
     expect(postResp.status()).toBe(200)
     const body = await postResp.json()