test(e2e): browser suite for the flows the server tests cannot see

Playwright under e2e/, its own npm project so Meteor never sees the dependency
(.meteorignore keeps the directory out of the bundle — a config file at the app
root is otherwise eagerly loaded into the server and crashes it).

Covers what the phase asked for: sign up / log in, creating a zone from the map
and watching the union get painted on /subscriptions and /zones, removing it
again, commenting on a fire, and switching language. The zone spec is the flow
that froze staging on 2026-07-30 — it passes only if the server is still
answering DDP while the union is recomputed.

docker-compose.e2e.yml is a throwaway stack (Mongo on tmpfs, no named volume) so
the destructive seeds cannot be pointed at anything real by accident;
playwright.config.js refuses to start against the staging or production domains.

i18n.spec.js leaves a test.fixme on a real bug found while writing it: the
language chosen in the profile does not survive a page reload.

e2e/playwright.config.js

@@ -0,0 +1,42 @@
+import { defineConfig, devices } from '@playwright/test';
+
+// E2E_BASE_URL points at a THROWAWAY stack — the compose in docker-compose.e2e.yml
+// or a local dev server. Never at testfuegos.comunes.org or anything else with
+// data in it: these tests create users and subscriptions, and the seed step wipes
+// collections.
+const baseURL = process.env.E2E_BASE_URL || 'http://localhost:3100';
+
+if (/testfuegos|fuegos\.comunes|fires\.comunes/.test(baseURL)) {
+  throw new Error(`Refusing to run the e2e suite against ${baseURL}: it seeds and writes data.`);
+}
+
+export default defineConfig({
+  testDir: './tests',
+  // Meteor's first page load compiles and ships a big bundle; the map then waits
+  // for tiles and DDP subscriptions.
+  timeout: 90 * 1000,
+  expect: { timeout: 20 * 1000 },
+  // Every spec creates its own user, but they share one Mongo and one union
+  // recompute queue; running them in parallel makes failures much harder to read
+  // for very little wall-clock on a runner that only has one job slot anyway.
+  workers: 1,
+  fullyParallel: false,
+  forbidOnly: !!process.env.CI,
+  retries: process.env.CI ? 1 : 0,
+  reporter: process.env.CI
+    ? [['list'], ['html', { open: 'never', outputFolder: 'playwright-report' }]]
+    : [['list']],
+  use: {
+    baseURL,
+    // Both on first retry only: a trace per test would be gigabytes of artifacts
+    // for a suite that is green most of the time.
+    trace: 'retain-on-failure',
+    screenshot: 'only-on-failure',
+    video: 'retain-on-failure',
+    actionTimeout: 20 * 1000,
+    locale: 'es-ES'
+  },
+  projects: [
+    { name: 'chromium', use: { ...devices['Desktop Chrome'] } }
+  ]
+});