feat: implement audit logging system with service, controller, and interceptor to track user actions across core services

prisma/schema.prisma

@@ -166,6 +166,9 @@ model User {
   // Verification actions (admin)
   verificationActions VerificationHistory[] @relation("VerificationActions")
 
+  // Audit Log (actor)
+  auditLogs         AuditLog[]
+
   @@index([email])
   @@index([role])
   @@index([status])
@@ -797,3 +800,27 @@ model VerificationHistory {
   @@index([createdAt])
   @@map("verification_history")
 }
+
+// ============================================
+// AUDIT LOG
+// ============================================
+model AuditLog {
+  id           String   @id @default(uuid())
+  actorId      String?              // null = system / unauthenticated
+  actorRole    String?              // USER, AGENT, ADMIN, SUPER_ADMIN, SYSTEM
+  action       String               // see AuditAction enum in audit.constants.ts
+  resourceType String?              // User, AgentProfile, Subscription, Payment, etc.
+  resourceId   String?
+  metadata     Json?                // { before, after, reason, params, ... }
+  ipAddress    String?
+  userAgent    String?
+  createdAt    DateTime @default(now())
+
+  actor User? @relation(fields: [actorId], references: [id], onDelete: SetNull)
+
+  @@index([actorId, createdAt])
+  @@index([resourceType, resourceId])
+  @@index([action, createdAt])
+  @@index([createdAt])
+  @@map("audit_logs")
+}