fix: go vet errors in observability metrics

- Remove unused avg variable in prometheus.go
- Fix import ordering in llm_metrics.go (move net/http to top)

internal/observability/prometheus.go

@@ -51,7 +51,6 @@ func (p *PrometheusExporter) exportTTFT(lines *[]string) {
 
 		model := extractModel(key)
 		sum := sumInt64(samples)
-		avg := sum / int64(len(samples))
 
 		// Export histogram buckets (in seconds)
 		buckets := []float64{0.001, 0.01, 0.05, 0.1, 0.5, 1.0, 5.0}

internal/proxy/llm_metrics.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"net/http"
 	"strings"
 	"time"
 
@@ -149,5 +150,4 @@ func (w *ResponseWriterWrapper) Hijack() (net.Conn, *bufio.ReadWriter, error) {
 	return nil, nil, fmt.Errorf("response writer does not implement Hijacker")
 }
 
-// Import http package
-import "net/http"
+