Add cluster demo script for easy cluster management

This script provides a convenient way to spawn and manage a ToastyFS cluster
for demo and testing purposes. Features include:

- Start a cluster with configurable number of chunk servers
- Automatic building if binary is not present
- Process management with PID tracking
- Status checking for all cluster nodes
- Easy cleanup of all cluster processes
- Separate log files for each server component
- Colorized output for better readability

Usage:
  ./scripts/cluster_demo.sh start [num_servers]  - Start cluster
  ./scripts/cluster_demo.sh stop                 - Stop cluster
  ./scripts/cluster_demo.sh status               - Show status
  ./scripts/cluster_demo.sh clean                - Clean data/logs

.gitignore

@@ -3,6 +3,7 @@
 *.o
 *.a
 chunk_server_data_*
+
 # Coverage reports
 coverage_report/
 *.gcov
@@ -10,3 +11,8 @@ coverage_report/
 *.gcno
 *.wal
 *.tmp
+
+# Cluster demo artifacts
+.cluster_demo.pids
+cluster_logs/
+cluster_data/