feat: implement critical security fixes for SQL injection and authentication vulnerabilities

Security Enhancements:
- Fix SQL injection vulnerabilities by replacing whereRaw queries with parameterized queries
- Add LIKE pattern escaping to prevent SQL injection in search functionality
- Implement account lockout protection (5 failed attempts = 30 min lockout)
- Add comprehensive login attempt tracking and audit trail
- Enhance JWT tokens with issuer validation, IP tracking, and password change detection
- Add logout endpoint and session management
- Prevent user enumeration with generic error messages

Database Changes:
- Add login_attempts table for authentication tracking
- Add security columns to admin_users (password_changed_at, last_login_ip, two_factor_enabled)

New Security Features:
- Brute force protection with configurable lockout duration
- Automatic cleanup of old login attempts
- Enhanced authentication middleware with stricter validation
- Monitoring scripts for security health checks

All fixes are backward compatible and production-ready with rollback plans included.

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

Co-Authored-By: Claude <[email protected]>

backend/migrations/016_add_auth_security_columns.js

@@ -0,0 +1,25 @@
+exports.up = function(knex) {
+  return knex.schema.table('admin_users', table => {
+    // Add password change tracking
+    table.timestamp('password_changed_at').nullable();
+    
+    // Add last login IP for security monitoring
+    table.string('last_login_ip', 45).nullable();
+    
+    // Add account security flags
+    table.boolean('two_factor_enabled').defaultTo(false);
+    table.string('two_factor_secret').nullable();
+    
+    // Add index for performance
+    table.index('password_changed_at');
+  });
+};
+
+exports.down = function(knex) {
+  return knex.schema.table('admin_users', table => {
+    table.dropColumn('password_changed_at');
+    table.dropColumn('last_login_ip');
+    table.dropColumn('two_factor_enabled');
+    table.dropColumn('two_factor_secret');
+  });
+};