Update minimum go version to 1.26.1, golangci-lint to 2.11.2, fix test style (#36876)

Hey, I bumped Go to 1.26.1 and fixed a couple of things I ran into while
poking around.

### Changes

- Bump go.mod from 1.26.0 to 1.26.1 (security patch)
- Bump golangci-lint from v2.10.1 to v2.11.2
- Run make tidy, fmt, lint-go

---------

Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Claude (Opus 4.6) <noreply@anthropic.com>

tests/integration/api_releases_test.go

@@ -422,7 +422,7 @@ func TestAPIUploadAssetRelease(t *testing.T) {
 		defer tests.PrintCurrentTest(t)()
 		const filename = "image.png"
 
-		performUpload := func(t *testing.T, uploadURL string, buf []byte, expectedStatus int) *httptest.ResponseRecorder {
+		performUpload := func(t *testing.T, uploadURL string, _ []byte, _ int) *httptest.ResponseRecorder {
 			body := &bytes.Buffer{}
 			writer := multipart.NewWriter(body)
 			part, err := writer.CreateFormFile("attachment", filename)