feat(sync): full code sync from release

backend/internal/domain/constants_test.go

@@ -0,0 +1,24 @@
+package domain
+
+import "testing"
+
+func TestDefaultAntigravityModelMapping_ImageCompatibilityAliases(t *testing.T) {
+	t.Parallel()
+
+	cases := map[string]string{
+		"gemini-3.1-flash-image":         "gemini-3.1-flash-image",
+		"gemini-3.1-flash-image-preview": "gemini-3.1-flash-image",
+		"gemini-3-pro-image":             "gemini-3.1-flash-image",
+		"gemini-3-pro-image-preview":     "gemini-3.1-flash-image",
+	}
+
+	for from, want := range cases {
+		got, ok := DefaultAntigravityModelMapping[from]
+		if !ok {
+			t.Fatalf("expected mapping for %q to exist", from)
+		}
+		if got != want {
+			t.Fatalf("unexpected mapping for %q: got %q want %q", from, got, want)
+		}
+	}
+}