Add missing tmpfs metric handling to system widget

- Add memory_tmp_usage_percent, memory_tmp_used_gb, memory_tmp_total_gb metric parsing
- Fix tmpfs display showing as —% —GB/—GB in dashboard
- System widget now properly receives and displays tmpfs metrics from memory collector

dashboard/src/ui/widgets/system.rs

@@ -357,6 +357,23 @@ impl Widget for SystemWidget {
                         self.memory_total_gb = Some(total);
                     }
                 }
+                
+                // Tmpfs metrics
+                "memory_tmp_usage_percent" => {
+                    if let MetricValue::Float(usage) = metric.value {
+                        self.tmp_usage_percent = Some(usage);
+                    }
+                }
+                "memory_tmp_used_gb" => {
+                    if let MetricValue::Float(used) = metric.value {
+                        self.tmp_used_gb = Some(used);
+                    }
+                }
+                "memory_tmp_total_gb" => {
+                    if let MetricValue::Float(total) = metric.value {
+                        self.tmp_total_gb = Some(total);
+                    }
+                }
                 _ => {}
             }
         }