test(web-next): e2e cross-feature sign-up→welcome-email flow

End-to-end proof-of-life. bindAllDevSeed wires InMemoryEventBus +
InMemoryJobQueue across all features. signUpController publishes
auth.user.signed-up; marketing-pages' handler enqueues
marketing-pages.send-welcome-email; the in-memory queue dispatches
the wrapped job which records on RecordingMailerService.

Adds ./di/container, ./di/symbols, ./services/mailer, and
./services/recording-mailer to auth + marketing-pages exports so
the e2e test can resolve from the per-feature containers without
deep-importing.

packages/auth/package.json

@@ -9,7 +9,9 @@
     "./cms": "./src/integrations/cms/index.ts",
     "./api": "./src/integrations/api/router.ts",
     "./di/bind-production": "./src/di/bind-production.ts",
-    "./di/bind-dev-seed": "./src/di/bind-dev-seed.ts"
+    "./di/bind-dev-seed": "./src/di/bind-dev-seed.ts",
+    "./di/container": "./src/di/container.ts",
+    "./di/symbols": "./src/di/symbols.ts"
   },
   "scripts": {
     "build": "tsc --noEmit",