FRE-5335 Hook waitlist signup to send confirmation email via Resend

- Added @shieldai/shared-notifications, bullmq, ioredis deps to API
- POST /api/waitlist/signup now sends waitlist_confirmation email via EmailService
- Schedules welcome sequence (day1 intro, day3 features, day7 launch teaser) via BullMQ delayed jobs
- Added waitlist email worker in @shieldai/jobs to process delayed welcome sequence emails
- Templates already in place: waitlist_confirmation, waitlist_intro, waitlist_features, waitlist_launch_teaser with dark-themed HTML layouts

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/api/package.json

@@ -20,9 +20,12 @@
     "@shieldai/db": "workspace:*",
     "@shieldai/monitoring": "workspace:*",
     "@shieldai/report": "workspace:*",
+    "@shieldai/shared-notifications": "workspace:*",
     "@shieldai/types": "workspace:*",
     "@shieldai/voiceprint": "workspace:*",
-    "fastify": "^5.2.0"
+    "bullmq": "^5.24.0",
+    "fastify": "^5.2.0",
+    "ioredis": "^5.4.0"
   },
   "devDependencies": {
     "@vitest/coverage-v8": "^4.1.5",