feat: Add runner health UI - unhealthy status display and CPU monitoring tile

- Add unhealthy status display on runners list page (yellow color when online but unhealthy)
- Add is_healthy field to RunnersStatusJSON API response
- Add CPUInfo struct to RunnerCapability for CPU load monitoring
- Add CPU tile to runner edit page showing load percentage and CPU count
- Add real-time JavaScript polling for CPU tile updates
- Add locale string for unhealthy status

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

modules/structs/actions_capabilities.go

@@ -21,6 +21,15 @@ type DiskInfo struct {
 	UsedPercent float64 `json:"used_percent"`
 }
 
+// CPUInfo holds CPU load information for a runner
+type CPUInfo struct {
+	NumCPU      int     `json:"num_cpu"`
+	LoadAvg1m   float64 `json:"load_avg_1m"`
+	LoadAvg5m   float64 `json:"load_avg_5m"`
+	LoadAvg15m  float64 `json:"load_avg_15m"`
+	LoadPercent float64 `json:"load_percent"`
+}
+
 // DistroInfo holds Linux distribution information
 type DistroInfo struct {
 	ID         string `json:"id,omitempty"`          // e.g., "ubuntu", "debian", "fedora"
@@ -52,6 +61,7 @@ type RunnerCapability struct {
 	Features         *CapabilityFeatures `json:"features,omitempty"`
 	Limitations      []string            `json:"limitations,omitempty"`
 	Disk             *DiskInfo           `json:"disk,omitempty"`
+	CPU              *CPUInfo            `json:"cpu,omitempty"`
 	Bandwidth        *BandwidthInfo      `json:"bandwidth,omitempty"`
 	SuggestedLabels  []string            `json:"suggested_labels,omitempty"`
 }