Extend reconciliation sources: firm-role and realty-derived group membership

Future extension of the reconciliation cron (PAR-99). Today the only sync source is LuckPerms groups (server-wide). treasury-api-plugin already consumes TreasuryApi + BusinessApi (and could take a RealtyApi), so explorer group membership could also be derived from:

• Business: firm proprietorship / financial-role employees → a per-firm or role-based explorer group.
• Realty: property ownership/tenancy → an explorer group.

Add these as additional source values alongside luckperms in explorer_group_member so each source reconciles independently. Per the user: "recon for treasury, realty and business."