fix(mail): add periodic cleanup timers and proper shutdown handling for bounce manager and delivery queue; avoid mutating maps during iteration and prune stale rate-limiter stats to prevent memory growth

ts/mail/delivery/classes.unified.rate.limiter.ts

@@ -231,7 +231,21 @@ export class UnifiedRateLimiter extends EventEmitter {
         this.domainCounters.delete(key);
       }
     }
-    
+
+    // Clean stale stats.byIp entries for IPs that no longer have active counters or blocks
+    for (const ip of Object.keys(this.stats.byIp)) {
+      if (!this.ipCounters.has(ip) && !(this.config.blocks && ip in this.config.blocks)) {
+        delete this.stats.byIp[ip];
+      }
+    }
+
+    // Clean stale stats.byPattern entries for patterns that no longer have active counters
+    for (const pattern of Object.keys(this.stats.byPattern)) {
+      if (!this.patternCounters.has(pattern)) {
+        delete this.stats.byPattern[pattern];
+      }
+    }
+
     // Update statistics
     this.updateStats();
   }