Fix memory export and workspace downloads (v1.47.115)

[AlphaHorizon-AI]

Fix 401 Unauthorized when downloading memory export ZIP files from Archives and binary files from File Explorer.

Summary of changes:

• Created \rontend/src/lib/fileDownload.ts\ with authenticated Axios download helper and JSON error blob extraction.
• Replaced standard unauthenticated <a href>\ download links in \rontend/src/pages/Archives.tsx\ and \rontend/src/pages/FileExplorer.tsx\ with authenticated download actions featuring loading spinners and error banner toasts.
• Added query parameter authentication fallback (?infrastructure_token=\ / ?token=) for GET/HEAD endpoints in \shogun/api/control_plane_auth.py\ and \shogun/api/infrastructure_auth.py.
• Bumped version to 1.47.115 (build 266) across \�ersion.json, \pyproject.toml, and \shogun/init.py.
• Rebuilt frontend distribution artifacts.

Validation:

• Red-team hardening tests passed (11/11)
• Frontend unit tests for fileDownload passed (4/4)
• Frontend security tests passed (14/14)
• Pre-push validation suite passed
• Production frontend build & bundle check passed