Make dashboard auth diagnostics ASCII-safe

[w287346141]

Summary

• make dashboard auth and LAN exposure diagnostics ASCII-safe for terminals that render symbols poorly
• keep the same auth behavior while removing non-ASCII punctuation from the 403 body, unauthorized page hint, and stderr warning
• add regression coverage for ASCII-safe dashboard auth and host warnings

Validation

• npm.cmd test -- --run tests/dashboard-auth-token.test.ts tests/dashboard-host-and-token.test.ts
• npm.cmd run lint
• npm.cmd run typecheck
• git diff --check
• push hook ran npm.cmd run verify