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/README.md

@@ -159,15 +159,34 @@ herodo your_service_script.rhai
 
 ## Prerequisites
 
-### Linux (zinit)
+### Linux (zinit/systemd)
 
-Make sure zinit is installed and running:
+The service manager automatically discovers running zinit servers and falls back to systemd if none are found.
+
+**For zinit (recommended):**
 
 ```bash
 # Start zinit with default socket
 zinit -s /tmp/zinit.sock init
+
+# Or with a custom socket path
+zinit -s /var/run/zinit.sock init
 ```
 
+**Socket Discovery:**
+The service manager will automatically find running zinit servers by checking:
+1. `ZINIT_SOCKET_PATH` environment variable (if set)
+2. Common socket locations: `/var/run/zinit.sock`, `/tmp/zinit.sock`, `/run/zinit.sock`, `./zinit.sock`
+
+**Custom socket path:**
+```bash
+# Set custom socket path
+export ZINIT_SOCKET_PATH=/your/custom/path/zinit.sock
+```
+
+**Systemd fallback:**
+If no zinit server is detected, the service manager automatically falls back to systemd.
+
 ### macOS (launchctl)
 
 No additional setup required - uses the built-in launchctl system.