Polish login help and sign-up validation

[dana-khaing]

Summary

• clear stale sessions immediately when API auth tokens are invalid
• make login-help reply email fields full-width and lock saved admin reply emails
• make sign-up phone number optional
• warn users when a sign-up username is already taken

Tests

• pnpm exec tsc --noEmit
• venv/bin/python manage.py test core.tests.AuthAPITests.test_register_creates_user_profile_and_returns_user_payload core.tests.AuthAPITests.test_register_allows_missing_phone_number core.tests.AuthAPITests.test_username_availability_warns_when_username_is_taken core.tests.AuthAPITests.test_username_availability_allows_unused_username --settings=flowbit_backend.test_settings

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Project	Deployment	Actions	Updated (UTC)
flowbit	Building	Preview, Comment	May 30, 2026 12:32pm

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