fix(lint): resolve 6 golangci-lint issues blocking CI

- safe/safe.go: pass context.Background() to slog.LogAttrs (SA1012)
- capture_fingerprint/main.go: wrap ln/raw Close() defers to swallow err
- capture_fingerprint/peek_conn.go, serve_h2.go: ignore bytes.Buffer.Write
  return (cannot fail)
- verify_fingerprint/main.go: wrap resp.Body.Close() defer

These were pre-existing issues on release/custom-0.1.114 also failing
on v0.1.114.1. Fixing now so the current CI run turns green.

backend/internal/pkg/safe/safe.go

@@ -7,6 +7,7 @@
 package safe
 
 import (
+	"context"
 	"log/slog"
 	"runtime/debug"
 )
@@ -61,5 +62,5 @@ func logPanic(event string, attrs []slog.Attr, panicValue any) {
 		slog.Any("panic", panicValue),
 		slog.String("stack", string(debug.Stack())),
 	)
-	slog.LogAttrs(nil, slog.LevelError, event+panicSuffix, logAttrs...)
+	slog.LogAttrs(context.Background(), slog.LevelError, event+panicSuffix, logAttrs...)
 }

backend/tools/capture_fingerprint/main.go

@@ -49,7 +49,7 @@ func main() {
 	if err != nil {
 		log.Fatalf("listen %s: %v", *addr, err)
 	}
-	defer ln.Close()
+	defer func() { _ = ln.Close() }()
 
 	logStartupBanner(*addr)
 	acceptLoop(ln, tlsCfg, *outFile)
@@ -80,7 +80,7 @@ func acceptLoop(ln net.Listener, tlsCfg *ctls.Config, outFile string) {
 }
 
 func handleConn(raw net.Conn, tlsCfg *ctls.Config, outFile string) {
-	defer raw.Close()
+	defer func() { _ = raw.Close() }()
 	_ = raw.SetDeadline(time.Now().Add(30 * time.Second))
 
 	capture := &Capture{

backend/tools/capture_fingerprint/peek_conn.go

@@ -27,7 +27,7 @@ func (p *peekConn) peek(n int) ([]byte, error) {
 	if _, err := io.ReadFull(p.Conn, chunk); err != nil {
 		return nil, err
 	}
-	p.buf.Write(chunk)
+	_, _ = p.buf.Write(chunk)
 	return chunk, nil
 }
 

backend/tools/capture_fingerprint/serve_h2.go

@@ -186,7 +186,7 @@ func (s *h2Session) handleData(f *http2.DataFrame) {
 		if len(data) > need {
 			data = data[:need]
 		}
-		buf.Write(data)
+		_, _ = buf.Write(data)
 	}
 	if f.StreamEnded() {
 		// Attach body preview back to the matching request.

backend/tools/verify_fingerprint/main.go

@@ -73,7 +73,7 @@ func main() {
 		fmt.Printf("check capture server log for ClientHello details\n")
 		return
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 	body, _ := io.ReadAll(resp.Body)
 	fmt.Printf("status=%d body=%s\n", resp.StatusCode, body)
 }