Add IP address search feature with global search box

- Add API endpoint GET /api/scans/by-ip/{ip_address} to retrieve
  last 10 scans containing a specific IP
- Add ScanService.get_scans_by_ip() method with ScanIP join query
- Add search box to global navigation header
- Create dedicated search results page at /search/ip
- Update API documentation with new endpoint

app/web/api/scans.py

@@ -281,6 +281,45 @@ def get_scan_status(scan_id):
         }), 500
 
 
+@bp.route('/by-ip/<ip_address>', methods=['GET'])
+@api_auth_required
+def get_scans_by_ip(ip_address):
+    """
+    Get last 10 scans containing a specific IP address.
+
+    Args:
+        ip_address: IP address to search for
+
+    Returns:
+        JSON response with list of scans containing the IP
+    """
+    try:
+        # Get scans from service
+        scan_service = ScanService(current_app.db_session)
+        scans = scan_service.get_scans_by_ip(ip_address)
+
+        logger.info(f"Retrieved {len(scans)} scans for IP: {ip_address}")
+
+        return jsonify({
+            'ip_address': ip_address,
+            'scans': scans,
+            'count': len(scans)
+        })
+
+    except SQLAlchemyError as e:
+        logger.error(f"Database error retrieving scans for IP {ip_address}: {str(e)}")
+        return jsonify({
+            'error': 'Database error',
+            'message': 'Failed to retrieve scans'
+        }), 500
+    except Exception as e:
+        logger.error(f"Unexpected error retrieving scans for IP {ip_address}: {str(e)}", exc_info=True)
+        return jsonify({
+            'error': 'Internal server error',
+            'message': 'An unexpected error occurred'
+        }), 500
+
+
 @bp.route('/<int:scan_id1>/compare/<int:scan_id2>', methods=['GET'])
 @api_auth_required
 def compare_scans(scan_id1, scan_id2):