Host-side identifier (systemd unit name and /var/lib/left4me dirs) is now
str(server.id), centralized in services/server_identity.server_unit_name.
Server.name becomes a free-form display label, required and unique per
user (was [a-z0-9_-]{1,64} and globally unique).
Migration 0006 swaps the old global UNIQUE(name) for UNIQUE(user_id, name).
Web routes already keyed on id; templates only used name for display.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
