refactor: rename Personal Pro to Skipper and Team Pro to Admiral (#256)

Align paid tier names with Sencho's nautical identity. Internal variant
values ('personal'/'team') remain unchanged in code, database, and
Lemon Squeezy integration — only user-facing display names updated.

- Backend: requireTeamPro → requireAdmiral, TEAM_PRO_REQUIRED → ADMIRAL_REQUIRED
- Frontend: TeamProGate.tsx → AdmiralGate.tsx, TierBadge labels updated
- Website: PricingSection tier names and nautical descriptions
- Docs: all 11 affected pages renamed, nautical footnote added to licensing

frontend/src/components/TierBadge.tsx

@@ -11,8 +11,8 @@ interface TierBadgeProps {
 
 const tierConfig = {
     community: { icon: Globe, label: 'Community' },
-    pro: { icon: Crown, label: 'Pro' },
-    team: { icon: Users, label: 'Team' },
+    pro: { icon: Crown, label: 'Skipper' },
+    team: { icon: Users, label: 'Admiral' },
 } as const;
 
 function resolveTier(tier: LicenseTier, variant: LicenseVariant, status: LicenseStatus) {