Accounts were created as 'Unknown' and the client never sends a name, so the admin
panel / friends / squad showed no names. Add SteamWebApiService (GetPlayerSummaries),
wired into LoginWithSteam to backfill the DisplayName from the Steam persona when it's
still 'Unknown'. Admin gets a LAN-only /admin/backfill-names action (+ button) to
backfill existing accounts in one shot. Key read from config SteamWebApiKey (Vault ->
env), inert when unset.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>