Bulk import accepted dots in frontend/backend/server names but UI and
backend validators rejected them with ^[a-zA-Z0-9_-]+$. After import,
entities with dots could not be edited. HAProxy itself allows dots in
section names, so the regex is expanded to ^[a-zA-Z0-9_.-]+$ across
all 12 validation points (5 React form rules, 1 ACL char-strip,
3 Pydantic validators, 1 WAF validator, 2 config-validator warnings).