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/settings/DeveloperSection.tsx

@@ -143,7 +143,7 @@ export function DeveloperSection({ settings, onSettingChange, onSave, isSaving,
                                 </div>
                             </div>
 
-                            {isPaid && license?.variant === 'team' && (
+                            {isPaid && license?.variant === 'admiral' && (
                                 <div className="flex items-center justify-between gap-4 pt-4 border-t border-glass-border">
                                     <div className="space-y-0.5">
                                         <Label className="text-base">Audit Log Retention</Label>