fix(ci): add stub RESEND_API_KEY + HELCIM_API_TOKEN to satisfy validate-env

server/plugins/validate-env.js process.exit(1)s on boot when these
are missing — the playwright job's 'Start server' step backgrounds
the process and returns instantly, so the crash was silent until
'Wait for server' timed out at 30s.

Stub values are safe: ALLOW_DEV_TEST_ENDPOINTS=true short-circuits
the Resend call in invite.post.js, and Helcim API calls are mocked
at the page.route level in join-flow.spec.js.

.forgejo/workflows/test.yml

@@ -29,6 +29,8 @@ jobs:
     env:
       MONGODB_URI: mongodb://localhost:27017/ghostguild-test
       JWT_SECRET: ci-test-jwt-secret
+      RESEND_API_KEY: re_ci_dummy_not_used
+      HELCIM_API_TOKEN: helcim_ci_dummy_not_used
       NUXT_PUBLIC_COMING_SOON: 'false'
       NODE_ENV: development
       ALLOW_DEV_TEST_ENDPOINTS: 'true'
@@ -81,6 +83,8 @@ jobs:
     env:
       MONGODB_URI: mongodb://localhost:27017/ghostguild-test
       JWT_SECRET: ci-test-jwt-secret
+      RESEND_API_KEY: re_ci_dummy_not_used
+      HELCIM_API_TOKEN: helcim_ci_dummy_not_used
       NUXT_PUBLIC_COMING_SOON: 'false'
       NODE_ENV: development
       ALLOW_DEV_TEST_ENDPOINTS: 'true'