fix: re-enable CI lint job and fix ~65 lint errors (partial)

Re-enable the golangci-lint job in CI (disabled Oct 2025), update to
Go 1.25 and golangci-lint-action v7. Fix errcheck, gosimple S1009,
staticcheck SA4031 and SA2001 errors across 54 files. Remaining ~39
lint errors will be addressed in follow-up commits.

config/config.go

@@ -397,7 +397,7 @@ func preventClose(text string) {
 	fmt.Println("\nFailed to start Erupe:\n" + text)
 	go wait()
 	fmt.Println("\nPress Enter/Return to exit...")
-	fmt.Scanln()
+	_, _ = fmt.Scanln()
 	os.Exit(0)
 }