Add automatic config file detection for dashboard TUI

- Dashboard now automatically looks for /etc/cm-dashboard/dashboard.toml
- No need to specify --config flag when using standard NixOS deployment
- Fallback to manual config path if default not found
- Update help text to reflect optional config parameter
- Simplifies dashboard usage - just run 'cm-dashboard' without arguments

dashboard/src/app.rs

@@ -28,13 +28,23 @@ impl Dashboard {
     pub async fn new(config_path: Option<String>, headless: bool) -> Result<Self> {
         info!("Initializing dashboard");
 
-        // Load configuration - config file is required
+        // Load configuration - try default path if not specified
         let config = match config_path {
             Some(path) => DashboardConfig::load_from_file(&path)?,
             None => {
-                error!("Configuration file is required. Use --config to specify path.");
-                error!("Dashboard configuration must be provided - no hardcoded defaults allowed.");
-                return Err(anyhow::anyhow!("Missing required configuration file"));
+                // Try default NixOS config path
+                let default_path = "/etc/cm-dashboard/dashboard.toml";
+                match DashboardConfig::load_from_file(default_path) {
+                    Ok(config) => {
+                        info!("Using default config file: {}", default_path);
+                        config
+                    }
+                    Err(e) => {
+                        error!("Configuration file is required. Use --config to specify path or ensure {} exists.", default_path);
+                        error!("Failed to load default config: {}", e);
+                        return Err(anyhow::anyhow!("Missing required configuration file"));
+                    }
+                }
             }
         };
 

dashboard/src/main.rs

@@ -20,7 +20,7 @@ struct Cli {
     #[arg(short, long, action = clap::ArgAction::Count)]
     verbose: u8,
 
-    /// Configuration file path (required)
+    /// Configuration file path (defaults to /etc/cm-dashboard/dashboard.toml)
     #[arg(short, long)]
     config: Option<String>,