fix(licensing): rename variant values to skipper/admiral and store resolved type (#379)

Rename internal variant values from 'personal'/'team' to 'skipper'/'admiral',
aligning code with user-facing tier names. Variant type is now resolved once
at activation/validation and stored in DB via license_variant_type, instead
of string-matching the Lemon Squeezy variant_name on every read. Also captures
variant_id for future lookups. Pre-existing installs auto-migrate on first
getVariant() call.

frontend/src/components/SettingsModal.tsx

@@ -303,7 +303,7 @@ export function SettingsModal({ isOpen, onClose, initialSection }: SettingsModal
         }
     };
 
-    const isAdmiral = isPaid && license?.variant === 'team';
+    const isAdmiral = isPaid && license?.variant === 'admiral';
 
     return (
         <Dialog open={isOpen} onOpenChange={(open) => !open && onClose()}>