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_token_test.go

@@ -502,11 +502,12 @@ func runTestCase(t *testing.T, testCase *requiredScopeTestCase, user *user_model
 			}
 			unauthorizedLevel := auth_model.Write
 			if categoryIsRequired {
-				if minRequiredLevel == auth_model.Read {
+				switch minRequiredLevel {
+				case auth_model.Read:
 					unauthorizedLevel = auth_model.NoAccess
-				} else if minRequiredLevel == auth_model.Write {
+				case auth_model.Write:
 					unauthorizedLevel = auth_model.Read
-				} else {
+				default:
 					assert.FailNow(t, "Invalid test case", "Unknown access token scope level: %v", minRequiredLevel)
 				}
 			}