Reject whitespace-only auth passwords

[bozicovichsantiago20-oss]

Summary

• Add a shared auth password validator requiring at least eight non-whitespace characters.
• Apply it to both registration and login schemas without trimming or rewriting valid submitted values.
• Add focused validator tests for whitespace-only and mixed-space passwords.
• Update the API test script to target test files so the package test command runs correctly.

Verification

• npm.cmd test -w apps/api
• node --test apps/api/src/tests/auth.test.js
• git diff --check

Closes #4186
Refs #743
/claim #4186