Enhance Mihomo proxy behavior and test coverage

- Updated the Mihomo proxy implementation to ensure the client Host header is removed from outgoing requests, preventing strict upstream servers from returning errors.
- Revised the test for Mihomo forwarding to verify that the Host header is correctly set and not forwarded to the upstream server, improving test reliability and coverage.

internal/proxy/mihomo.go

@@ -26,17 +26,21 @@ func NewMihomoForward(
 	}
 	rp := &httputil.ReverseProxy{
 		Rewrite: func(pr *httputil.ProxyRequest) {
-			NormalizeRequestURLPath(pr.In)
-			p := pr.In.URL.Path
+			// Нормализуем Out, не In (контракт httputil.ProxyRequest: In не трогать).
+			NormalizeRequestURLPath(pr.Out)
+			p := pr.Out.URL.Path
 			if !strings.HasPrefix(p, stripPrefix) {
 				return
 			}
 			rest := strings.TrimPrefix(strings.TrimPrefix(p, stripPrefix), "/")
 			dest := JoinPathPrefix(target, "/", rest)
 			du := *dest
-			du.RawQuery = pr.In.URL.RawQuery
+			du.RawQuery = pr.Out.URL.RawQuery
 			out := pr.Out
 			out.URL = &du
+			// Как в NewAliasForward: не оставлять Host клиента ни в поле, ни в Header —
+			// иначе строгий upstream (в т.ч. Mihomo) часто отвечает 400.
+			out.Header.Del("Host")
 			out.Host = du.Host
 			out.RequestURI = ""
 			out.Proto = "HTTP/1.1"

internal/proxy/mihomo_test.go

@@ -21,11 +21,15 @@ func TestMihomoForwardRewritesPathAndAuth(t *testing.T) {
 		t.Fatal(err)
 	}
 	req.Header.Set("Authorization", "Bearer client-should-not-forward")
+	req.Header.Set("Host", "public-gateway.example:8888")
 	h.ServeHTTP(httptest.NewRecorder(), req)
 
 	if cap.got == nil {
 		t.Fatal("no outgoing request captured")
 	}
+	if got, want := cap.got.Host, "127.0.0.1:9090"; got != want {
+		t.Fatalf("Host: got %q want %q (upstream must not see client Host)", got, want)
+	}
 	if got := cap.got.Header.Get("Authorization"); got != "Bearer testsecret" {
 		t.Fatalf("Authorization: got %q want Bearer testsecret", got)
 	}