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/context/LicenseContext.tsx

@@ -4,7 +4,7 @@ import { apiFetch } from '@/lib/api';
 export type LicenseTier = 'community' | 'paid';
 export type LicenseStatus = 'community' | 'trial' | 'active' | 'expired' | 'disabled';
 
-export type LicenseVariant = 'personal' | 'team' | null;
+export type LicenseVariant = 'skipper' | 'admiral' | null;
 
 export interface LicenseInfo {
     tier: LicenseTier;