Remove unused code and eliminate compiler warnings

- Remove unused fields from CommandStatus variants
- Clean up unused methods and unused collector fields
- Fix lifetime syntax warning in SystemWidget
- Delete unused cache module completely
- Remove redundant render methods from widgets

All agent and dashboard warnings eliminated while preserving
panel switching and scrolling functionality.

agent/src/collectors/systemd.rs

@@ -42,7 +42,6 @@ struct ServiceStatusInfo {
     load_state: String,
     active_state: String,
     sub_state: String,
-    description: String,
 }
 
 impl SystemdCollector {
@@ -170,18 +169,12 @@ impl SystemdCollector {
                 let load_state = fields.get(1).unwrap_or(&"unknown").to_string();
                 let active_state = fields.get(2).unwrap_or(&"unknown").to_string();
                 let sub_state = fields.get(3).unwrap_or(&"unknown").to_string();
-                let description = if fields.len() > 4 {
-                    fields[4..].join(" ")
-                } else {
-                    "".to_string()
-                };
 
                 // Cache the status information
                 status_cache.insert(service_name.to_string(), ServiceStatusInfo {
                     load_state: load_state.clone(),
                     active_state: active_state.clone(),
                     sub_state: sub_state.clone(),
-                    description,
                 });
 
                 all_service_names.insert(service_name.to_string());
@@ -432,9 +425,6 @@ impl SystemdCollector {
 
 #[async_trait]
 impl Collector for SystemdCollector {
-    fn name(&self) -> &str {
-        "systemd"
-    }
 
     async fn collect(&self, _status_tracker: &mut StatusTracker) -> Result<Vec<Metric>, CollectorError> {
         let start_time = Instant::now();