Implement contribution reminder scheduler using BullMQ

[Mona-i]

Problem

The package.json includes bullmq and ioredis but they are not wired up anywhere in the codebase. One of the most important features for cooperative groups is automated reminders when a member's monthly contribution is due — currently there is no scheduler at all.

Task

Implement a contribution reminder system:

1. Create src/modules/notifications/reminder.queue.ts
   Set up a BullMQ queue called contribution-reminders.
2. Create src/modules/notifications/reminder.processor.ts

A BullMQ worker that:

Receives job payload: { groupId, memberAddress, period, dueDate }
Calls NotificationsService.create(memberAddress, 'contribution_due', ...)
(Optional) Sends email if member has email on file (stub it with a TODO comment)

3. Schedule reminder jobs
   In a @Cron(CronExpression.EVERY_DAY_AT_9AM) job:

• For each active group, check its contribution_period_days from governance rules
• For each member not yet contributed in current period
• Enqueue a reminder job 3 days before contribution is due

4. Redis config

Add Redis connection to AppModule using BullModule.forRoot().

Acceptance Criteria

• BullMQ queue and processor implemented
• Daily cron job enqueues reminders for due-soon members
• Notification record created in DB when job runs
• Redis connection configurable via REDIS_URL env var
• Queue can be monitored (add bull-board or log queue stats)
• Unit test: mock queue, verify jobs enqueued correctly

[Vyacheslav-Tomashevskiy]

Claiming this one. Submitted #13.

• BullMQ contribution-reminders queue + ReminderProcessor, and a @Cron(CronExpression.EVERY_DAY_AT_9AM) ReminderScheduler that enqueues one reminder per active member who has not contributed in the current period, once the due date is within the lead window.
• Each job creates a contribution_due Notification via NotificationsService.create(...) (email stubbed with a // TODO nodemailer note).
• Redis wired from REDIS_URL via BullModule.forRoot(); queue counts logged for monitoring; deterministic jobId → one reminder per member per period.
• Unit test with a mocked queue + Prisma (enqueue / outside-window / already-contributed).

Since the schema has no per-group period field yet, period length is configurable via CONTRIBUTION_PERIOD_DAYS (default 30) and derived from group.createdAt, isolated so a governance value can drop in later.