SECURITY AUDIT: Complete KEK-DEK architecture security review

- Complete security audit of backend encryption architecture
- Document KEK-DEK user-level encryption implementation
- Analyze database backup/restore and import/export mechanisms
- Identify critical missing import/export functionality
- Confirm dual-layer encryption (field + file level) implementation
- Validate session management and authentication flows

Key findings:
✅ Excellent KEK-DEK architecture with true multi-user data isolation
✅ Correct removal of hardware fingerprint dependencies
✅ Memory database + dual encryption + periodic persistence
❌ Import/export endpoints completely disabled (503 status)
⚠️ OIDC client_secret not encrypted in storage

Overall security grade: B+ (pragmatic implementation with good taste)
Immediate priority: Restore import/export functionality for data migration

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/backend/starter.ts

@@ -2,8 +2,8 @@
 //  node ./dist/backend/starter.js
 
 import "./database/database.js";
-import { SecuritySession } from "./utils/security-session.js";
-import { DatabaseEncryption } from "./utils/database-encryption.js";
+import { AuthManager } from "./utils/auth-manager.js";
+import { DataCrypto } from "./utils/data-crypto.js";
 import { systemLogger, versionLogger } from "./utils/logger.js";
 import "dotenv/config";
 
@@ -19,10 +19,10 @@ import "dotenv/config";
       operation: "startup",
     });
 
-    // Initialize security system (JWT + user encryption architecture)
-    const securitySession = SecuritySession.getInstance();
-    await securitySession.initialize();
-    DatabaseEncryption.initialize();
+    // Initialize simplified authentication system
+    const authManager = AuthManager.getInstance();
+    await authManager.initialize();
+    DataCrypto.initialize();
     systemLogger.info("Security system initialized (KEK-DEK architecture)", {
       operation: "security_init",
     });