Fix service metrics not showing - remove cache check

The service_status_cache from discovery only has active_state with
all detailed metrics set to None. During collection, get_service_status()
was returning cached data instead of fetching fresh systemctl show data.

Now always fetch fresh data to populate memory_bytes, restart_count,
and uptime_seconds properly.

agent/src/collectors/systemd.rs

@@ -353,16 +353,12 @@ impl SystemdCollector {
         Ok((services, status_cache))
     }
 
-    /// Get service status from cache (if available) or fallback to systemctl
+    /// Get service status with detailed metrics from systemctl
     fn get_service_status(&self, service: &str) -> Result<ServiceStatusInfo> {
-        // Try to get status from cache first
-        if let Ok(state) = self.state.read() {
-            if let Some(cached_info) = state.service_status_cache.get(service) {
-                return Ok(cached_info.clone());
-            }
-        }
+        // Always fetch fresh data to get detailed metrics (memory, restarts, uptime)
+        // Note: Cache in service_status_cache only has basic active_state from discovery,
+        // with all detailed metrics set to None. We need fresh systemctl show data.
 
-        // Fallback to systemctl if not in cache (with 2 second timeout)
         let output = Command::new("timeout")
             .args(&[
                 "2",