fix(auth): validate debug sms phone strings

[aiirvizionz]

Summary

• reject non-string or blank testPhoneNumber values before diagnostics or Supabase work
• trim valid phone values before sending the debug OTP and redacting the response
• add regression coverage for numeric and whitespace-only payloads

Verification

• node node_modules\\vitest\\vitest.mjs run --config %TEMP%\\qryptchat-vitest-minimal.config.mjs "src/app/api/auth/debug-sms-config/route.test.js"
• git diff --check

This is a focused validation fix for the development-only SMS diagnostics endpoint.