Remove hardcoded --platform=linux/amd64 from Dockerfile so buildx produces
native arm64 images for Apple Silicon and Raspberry Pi. Add audit logging
for auth events, harden file storage with extension whitelists and
double-extension attack prevention, reject null-byte buffers in validation,
add data-testid attributes to all tool settings components, update
deployment docs with architecture notes and correct CI workflow references,
and fix unit test mock to match throwWithMessage error extraction.
Adds ensureStorageDir, saveFile, deleteStoredFile, and getStoredFilePath
utilities that manage the lifecycle of files on the local filesystem
under FILES_STORAGE_PATH.
Siddharth Kumar Sah