feat: add repository pattern, service layer architecture, and scheduler management

- Implement repository pattern for data access layer
- Add comprehensive service layer for business logic
- Create scheduler management system with health monitoring
- Add bounded buffer utility for memory management
- Enhance security audit logging with retention policies

lib/services/SecurityEventProcessor.ts

@@ -0,0 +1,87 @@
+import { SECURITY_MONITORING, TIME } from "../constants";
+import {
+  type AuditLogContext,
+  type AuditOutcome,
+  AuditSeverity,
+  type SecurityEventType,
+} from "../securityAuditLogger";
+import { BoundedBuffer } from "../utils/BoundedBuffer";
+
+export interface SecurityEventData {
+  timestamp: Date;
+  eventType: SecurityEventType;
+  context: AuditLogContext;
+  outcome: AuditOutcome;
+  severity: AuditSeverity;
+}
+
+/**
+ * Handles security event processing and buffering
+ * Single Responsibility: Event collection and storage
+ */
+export class SecurityEventProcessor {
+  private eventBuffer: BoundedBuffer<SecurityEventData>;
+
+  constructor() {
+    this.eventBuffer = new BoundedBuffer<SecurityEventData>({
+      maxSize: SECURITY_MONITORING.EVENT_BUFFER_MAX_SIZE,
+      retentionTime: SECURITY_MONITORING.EVENT_RETENTION_HOURS * TIME.HOUR,
+      cleanupThreshold: 0.9,
+    });
+  }
+
+  /**
+   * Add security event to buffer
+   */
+  addEvent(
+    eventType: SecurityEventType,
+    outcome: AuditOutcome,
+    context: AuditLogContext,
+    severity: AuditSeverity = AuditSeverity.INFO
+  ): void {
+    this.eventBuffer.push({
+      timestamp: new Date(),
+      eventType,
+      context,
+      outcome,
+      severity,
+    });
+  }
+
+  /**
+   * Get events within time range
+   */
+  getEventsWithinTime(timeRangeMs: number): SecurityEventData[] {
+    return this.eventBuffer.getWithinTime(timeRangeMs);
+  }
+
+  /**
+   * Get recent events for analysis
+   */
+  getRecentEvents(): SecurityEventData[] {
+    return this.eventBuffer.getWithinTime(
+      SECURITY_MONITORING.THREAT_DETECTION_WINDOW
+    );
+  }
+
+  /**
+   * Manual cleanup of old events
+   */
+  cleanup(): void {
+    this.eventBuffer.cleanup();
+  }
+
+  /**
+   * Get current buffer statistics
+   */
+  getStats(): {
+    bufferSize: number;
+    eventsCount: number;
+  } {
+    const recentEvents = this.getRecentEvents();
+    return {
+      bufferSize: SECURITY_MONITORING.EVENT_BUFFER_MAX_SIZE,
+      eventsCount: recentEvents.length,
+    };
+  }
+}