refactor(frontend): replace Axios with the Fetch API

Summary

opencti-front declares a direct dependency on axios (1.20.0) that is used in only four places, all of them loading stored file content from /storage/view/.... The native fetch API covers these cases, so the dependency can be dropped from the front end.

Current usage

File	What it loads
src/private/components/common/files/workbench/WorkbenchFileContent.jsx	workbench bundle (JSON)
src/private/components/common/stix_core_objects/StixCoreObjectContent.jsx	content file (text)
src/private/components/common/stix_core_objects/StixCoreObjectFileExport.tsx	content file (text)
src/private/components/settings/exclusion_lists/ExclusionListEdition.tsx	exclusion list file (text)

All four call Axios.get(url) and read res.data.

Proposal

• Replace those four calls with fetch, checking Response.ok explicitly and reading the body as JSON or text depending on the caller.
• Remove axios from the dependencies of opencti-front/package.json.
• Keep the axios entry in resolutions: axios is still pulled in transitively by the i18n-auto-translation dev dependency, and the resolution keeps that version pinned.

Scope

Front end only. The back end also uses axios, and that part is tracked separately — it was covered together with the front end in #15431, which this issue splits.