Add fetch/conversion metrics and improve logging

FetchResult now includes:
- StatusCode: HTTP status from upstream
- FetchDurationMs: time to fetch from upstream
- RemoteAddr: upstream server address

SourceMetadata now stores:
- ContentLength: size from upstream
- FetchDurationMs: fetch timing
- RemoteAddr: for debugging

Image conversion log now includes:
- host: source hostname (was missing)
- path: source path (renamed from file)
- convert_ms: image processing time
- quality: requested quality setting
- fit: requested fit mode

internal/imgcache/service.go

@@ -157,18 +157,23 @@ func (s *Service) fetchAndProcess(ctx context.Context, req *ImageRequest) (*Imag
 	}
 
 	// Process the image
+	processStart := time.Now()
+
 	processResult, err := s.processor.Process(ctx, bytes.NewReader(sourceData), req)
 	if err != nil {
 		return nil, fmt.Errorf("image processing failed: %w", err)
 	}
 
+	processDuration := time.Since(processStart)
+
 	// Log conversion details
 	inputSize := int64(len(sourceData))
 	outputSize := processResult.ContentLength
 	sizePercent := float64(outputSize) / float64(inputSize) * 100.0 //nolint:mnd // percentage calculation
 
 	s.log.Info("image converted",
-		"file", req.SourcePath,
+		"host", req.SourceHost,
+		"path", req.SourcePath,
 		"input_format", processResult.InputFormat,
 		"output_format", req.Format,
 		"input_bytes", inputSize,
@@ -176,6 +181,9 @@ func (s *Service) fetchAndProcess(ctx context.Context, req *ImageRequest) (*Imag
 		"input_dimensions", fmt.Sprintf("%dx%d", processResult.InputWidth, processResult.InputHeight),
 		"output_dimensions", fmt.Sprintf("%dx%d", processResult.Width, processResult.Height),
 		"size_ratio", fmt.Sprintf("%.1f%%", sizePercent),
+		"convert_ms", processDuration.Milliseconds(),
+		"quality", req.Quality,
+		"fit", req.FitMode,
 	)
 
 	// Store output content to cache