feat: Enhance service manager with zinit socket discovery and systemd fallback

- Improve Linux support by automatically discovering zinit sockets
  using environment variables and common paths.
- Add fallback to systemd if no zinit server is detected.
- Enhance README with detailed instructions for zinit usage,
  including custom socket path configuration.
- Add example demonstrating zinit socket discovery.
- Add logging to show socket discovery process.
- Add unit tests for service manager creation and socket discovery.

service_manager/examples/service_spaghetti.rs

@@ -10,6 +10,9 @@ use std::thread;
 use std::time::Duration;
 
 fn main() {
+    // Initialize logging to see socket discovery in action
+    env_logger::init();
+
     let manager = match create_service_manager() {
         Ok(manager) => manager,
         Err(e) => {

service_manager/examples/simple_service.rs

@@ -4,6 +4,9 @@ use std::thread;
 use std::time::Duration;
 
 fn main() {
+    // Initialize logging to see socket discovery in action
+    env_logger::init();
+
     // 1. Create a service manager for the current platform
     let manager = match create_service_manager() {
         Ok(manager) => manager,

service_manager/examples/socket_discovery_test.rs

@@ -0,0 +1,47 @@
+//! Socket Discovery Test
+//!
+//! This example demonstrates the zinit socket discovery functionality.
+//! It shows how the service manager finds available zinit sockets.
+
+use sal_service_manager::create_service_manager;
+
+fn main() {
+    // Initialize logging to see socket discovery in action
+    env_logger::init();
+    
+    println!("=== Zinit Socket Discovery Test ===");
+    println!("This test demonstrates how the service manager discovers zinit sockets.");
+    println!();
+    
+    // Test environment variable
+    if let Ok(socket_path) = std::env::var("ZINIT_SOCKET_PATH") {
+        println!("🔍 ZINIT_SOCKET_PATH environment variable set to: {}", socket_path);
+    } else {
+        println!("🔍 ZINIT_SOCKET_PATH environment variable not set");
+    }
+    println!();
+    
+    println!("🚀 Creating service manager...");
+    match create_service_manager() {
+        Ok(_manager) => {
+            println!("✅ Service manager created successfully!");
+            
+            #[cfg(target_os = "macos")]
+            println!("📱 Platform: macOS - Using launchctl");
+            
+            #[cfg(target_os = "linux")]
+            println!("🐧 Platform: Linux - Check logs above for socket discovery details");
+        }
+        Err(e) => {
+            println!("❌ Failed to create service manager: {}", e);
+        }
+    }
+    
+    println!();
+    println!("=== Test Complete ===");
+    println!();
+    println!("To test zinit socket discovery on Linux:");
+    println!("1. Start zinit: zinit -s /tmp/zinit.sock init");
+    println!("2. Run with logging: RUST_LOG=debug cargo run --example socket_discovery_test -p sal-service-manager");
+    println!("3. Or set custom path: ZINIT_SOCKET_PATH=/custom/path.sock RUST_LOG=debug cargo run --example socket_discovery_test -p sal-service-manager");
+}