fix: Add hasCPU/hasNVMe flags to prevent false 'no CPU sensor' errors

Addresses #101

v4.23.0 introduced a regression where systems with only NVMe temperatures
(no CPU sensor) would display "No CPU sensor" in the UI. This was caused
by the Available flag being set to true when NVMe temps existed, even
without CPU data, triggering the error message in the frontend.

Backend changes:
- Add HasCPU and HasNVMe boolean fields to Temperature model
- Extend CPU sensor detection to support more chip types: zenpower,
  k8temp, acpitz, it87 (case-insensitive matching)
- HasCPU is set based on CPU chip detection (coretemp, k10temp, etc.),
  not value thresholds
- This prevents false negatives when sensors report 0°C during resets
- CPU temperature values now accepted even when 0 (checked with !IsNaN
  instead of > 0)
- extractTempInput returns NaN instead of 0 when no data found
- Available flag means "any temperature data exists" for backward compatibility
- Update mock generator to properly set the new flags
- Add unit tests for NVMe-only and 0°C scenarios to prevent regression
- Removed amd_energy from CPU chip list (power sensor, not temperature)

Frontend changes:
- Add hasCPU and hasNVMe optional fields to Temperature interface
- Update NodeSummaryTable to check hasCPU flag with fallback to available
  for backward compatibility with older API responses
- Update NodeCard temperature display logic with same fallback pattern
- Systems with only NVMe temps now show "-" instead of error message
- Fallback ensures UI works with both old and new API responses

Testing:
- All unit tests pass including NVMe-only and 0°C test cases
- Fix prevents false "no CPU sensor" errors when sensors temporarily report 0°C
- Fix eliminates false "no CPU sensor" errors for NVMe-only systems

internal/monitoring/temperature.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"math"
 	"os/exec"
 	"strconv"
 	"strings"
@@ -153,6 +154,8 @@ func (tc *TemperatureCollector) parseSensorsJSON(jsonStr string) (*models.Temper
 		NVMe:  []models.NVMeTemp{},
 	}
 
+	foundCPUChip := false
+
 	// Parse each sensor chip
 	for chipName, chipData := range sensorsData {
 		chipMap, ok := chipData.(map[string]interface{})
@@ -160,8 +163,15 @@ func (tc *TemperatureCollector) parseSensorsJSON(jsonStr string) (*models.Temper
 			continue
 		}
 
-		// Handle CPU temperature sensors (coretemp, k10temp, etc.)
-		if strings.Contains(chipName, "coretemp") || strings.Contains(chipName, "k10temp") {
+		// Handle CPU temperature sensors
+		chipLower := strings.ToLower(chipName)
+		if strings.Contains(chipLower, "coretemp") ||
+		   strings.Contains(chipLower, "k10temp") ||
+		   strings.Contains(chipLower, "zenpower") ||
+		   strings.Contains(chipLower, "k8temp") ||
+		   strings.Contains(chipLower, "acpitz") ||
+		   strings.Contains(chipLower, "it87") {
+			foundCPUChip = true
 			tc.parseCPUTemps(chipMap, temp)
 		}
 
@@ -180,11 +190,13 @@ func (tc *TemperatureCollector) parseSensorsJSON(jsonStr string) (*models.Temper
 		}
 	}
 
-	if temp.CPUPackage > 0 || temp.CPUMax > 0 || len(temp.Cores) > 0 || len(temp.NVMe) > 0 {
-		temp.Available = true
-	} else {
-		temp.Available = false
-	}
+	// Set individual sensor type flags based on chip presence, not value thresholds
+	// This prevents false negatives when sensors report 0°C during resets or temporarily
+	temp.HasCPU = foundCPUChip
+	temp.HasNVMe = len(temp.NVMe) > 0
+
+	// Available means any temperature data exists (backward compatibility)
+	temp.Available = temp.HasCPU || temp.HasNVMe
 
 	return temp, nil
 }
@@ -199,7 +211,7 @@ func (tc *TemperatureCollector) parseCPUTemps(chipMap map[string]interface{}, te
 
 		// Look for Package id (Intel) or Tdie (AMD)
 		if strings.Contains(sensorName, "Package id") || strings.Contains(sensorName, "Tdie") {
-			if tempVal := extractTempInput(sensorMap); tempVal > 0 {
+			if tempVal := extractTempInput(sensorMap); !math.IsNaN(tempVal) {
 				temp.CPUPackage = tempVal
 			}
 		}
@@ -207,7 +219,7 @@ func (tc *TemperatureCollector) parseCPUTemps(chipMap map[string]interface{}, te
 		// Look for individual cores
 		if strings.HasPrefix(sensorName, "Core ") {
 			coreNum := extractCoreNumber(sensorName)
-			if tempVal := extractTempInput(sensorMap); tempVal > 0 {
+			if tempVal := extractTempInput(sensorMap); !math.IsNaN(tempVal) {
 				temp.Cores = append(temp.Cores, models.CoreTemp{
 					Core: coreNum,
 					Temp: tempVal,
@@ -233,7 +245,7 @@ func (tc *TemperatureCollector) parseNVMeTemps(chipName string, chipMap map[stri
 
 		// Look for Composite temperature (main NVMe temp)
 		if strings.Contains(sensorName, "Composite") || strings.Contains(sensorName, "Sensor 1") {
-			if tempVal := extractTempInput(sensorMap); tempVal > 0 {
+			if tempVal := extractTempInput(sensorMap); !math.IsNaN(tempVal) && tempVal > 0 {
 				temp.NVMe = append(temp.NVMe, models.NVMeTemp{
 					Device: device,
 					Temp:   tempVal,
@@ -261,7 +273,7 @@ func extractTempInput(sensorMap map[string]interface{}) float64 {
 			}
 		}
 	}
-	return 0
+	return math.NaN()
 }
 
 // extractCoreNumber extracts the core number from a sensor name like "Core 0"