feat(listener): add automatic cleanup service for events and DB rows

[susanyusuf]

Closes #100
Closes #63
Closes #179
Closes #177

Description 1. listener/src/services/cleanup-service.ts (new file)

Introduced a Cleanup Service class that runs on a configurable
interval and deletes stale database rows from two tables:

• scheduled_notifications — removes entries with status
  COMPLETED, FAILED, or CANCELLED older than the configured
  retention period (default: 7 days)
• rate_limit_events — removes audit rows older than the
  configured retention period (default: 24 hours)

Also delegates in-memory event pruning to EventRegistry via
startCleanup() / stopCleanup().

Bug fixed: logger.info('CleanupService started', this.config)
caused a TypeScript compile error because CleanupConfig
an index signature required by the logger's Record string,
Record<string, unknown> parameter type. Fixed with
this.config as unknown as Record<string, unknown.

2. listener/src/services/cleanup-service.test.ts (new file)

Test suite covering:

• EventRegistry TTL pruning (expired events removed, fresh
  events kept, interval start/stop)
• CleanupService DB cleanup (correct SQL fired, interval
  behavior, idempotent start(), clean stop())

3. listener/src/store/event-registry.ts

Extended EventRegistry to support TTL-based expiry:

• Added ttlMs constructor parameter (default: 24 hours)
• Added pruneExpired() — filters out events whose receivedAt
  timestamp is older than ttlMs
• Added startCleanup(intervalMs) / stopCleanup() — controls a
  self-managed setInterval for automatic pruning

4. listener/src/types/index.ts

Added the AppCleanupConfig interface defining four configurable
retention/interval values:

• intervalMs — how often cleanup runs
• notificationRetentionMs — how long to keep old notifications
  in the DB
• rateLimitEventRetentionMs — how long to keep rate-limit audit
  rows
• eventRetentionMs — how long to keep in-memory events

Also added cleanup?: AppCleanupConfig to the main Config
interface.
5. listener/src/config.ts

Added loadCleanupConfig() which reads the four new retention
values from environment variables (CLEANUP_INTERVAL_MS,
NOTIFICATION_RETENTION_MS, RATE_LIMIT_EVENT_RETENTION_MS,
EVENT_RETENTION_MS) with sensible defaults. The result is
merged into the main config object returned by loadConfig().
6. listener/src/index.ts

Wired CleanupService into the application lifecycle:

• Instantiated after DB initialization, using config.cleanup
  settings
• cleanupService.start() called at boot
• cleanupService.stop() called during graceful shutdown
  alongside other services
• The EventRegistry's ttlMs is also overridden at startup from
  config before the service starts

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@susanyusuf Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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