ci: add golangci-lint config and fix formatting

- Add .golangci.yml with minimal linters (govet, ineffassign)
- Run gofmt -s and goimports on all files to fix formatting
- Disable fieldalignment and copylocks checks in govet

internal/progress/estimator.go

@@ -42,11 +42,11 @@ func (e *ETAEstimator) GetETA() time.Duration {
 	if e.itemsComplete == 0 || e.totalItems == 0 {
 		return 0
 	}
-	
+
 	elapsed := e.GetElapsed()
 	avgTimePerItem := elapsed / time.Duration(e.itemsComplete)
 	remainingItems := e.totalItems - e.itemsComplete
-	
+
 	return avgTimePerItem * time.Duration(remainingItems)
 }
 
@@ -83,12 +83,12 @@ func (e *ETAEstimator) GetFullStatus(baseMessage string) string {
 		// No items to track, just show elapsed
 		return fmt.Sprintf("%s | Elapsed: %s", baseMessage, e.FormatElapsed())
 	}
-	
+
 	if e.itemsComplete == 0 {
 		// Just started
 		return fmt.Sprintf("%s | 0/%d | Starting...", baseMessage, e.totalItems)
 	}
-	
+
 	// Full status with progress and ETA
 	return fmt.Sprintf("%s | %s | Elapsed: %s | ETA: %s",
 		baseMessage,
@@ -102,44 +102,44 @@ func FormatDuration(d time.Duration) string {
 	if d < time.Second {
 		return "< 1s"
 	}
-	
+
 	hours := int(d.Hours())
 	minutes := int(d.Minutes()) % 60
 	seconds := int(d.Seconds()) % 60
-	
+
 	if hours > 0 {
 		if minutes > 0 {
 			return fmt.Sprintf("%dh %dm", hours, minutes)
 		}
 		return fmt.Sprintf("%dh", hours)
 	}
-	
+
 	if minutes > 0 {
 		if seconds > 5 { // Only show seconds if > 5
 			return fmt.Sprintf("%dm %ds", minutes, seconds)
 		}
 		return fmt.Sprintf("%dm", minutes)
 	}
-	
+
 	return fmt.Sprintf("%ds", seconds)
 }
 
 // EstimateSizeBasedDuration estimates duration based on size (fallback when no progress tracking)
 func EstimateSizeBasedDuration(sizeBytes int64, cores int) time.Duration {
 	sizeMB := float64(sizeBytes) / (1024 * 1024)
-	
+
 	// Base estimate: ~100MB per minute on average hardware
 	baseMinutes := sizeMB / 100.0
-	
+
 	// Adjust for CPU cores (more cores = faster, but not linear)
 	// Use square root to represent diminishing returns
 	if cores > 1 {
 		speedup := 1.0 + (0.3 * (float64(cores) - 1)) // 30% improvement per core
 		baseMinutes = baseMinutes / speedup
 	}
-	
+
 	// Add 20% buffer for safety
 	baseMinutes = baseMinutes * 1.2
-	
+
 	return time.Duration(baseMinutes * float64(time.Minute))
 }