feat: add license activation system with feature gates

- License key generator tool at ~/Desktop/LicenseGenerator
- Backend validator route (GET /api/license/status, POST /api/license/activate)
- Activation page in sidebar with status, key input, and free/premium feature list
- useLicense hook for frontend license state
- Feature gates: premium eligibility buttons (DDMA, DeltaIns, Tufts, United, CCA) disabled without license
- Feature gates: premium claim buttons (CCA, Delta MA, United, Tufts) and all PreAuth buttons disabled without license
- Free features always active: MassHealth eligibility/claim, Documents, Payments, Backups, Reports
- README: license key generator usage instructions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/Frontend/src/components/layout/sidebar.tsx

@@ -186,6 +186,12 @@ export function Sidebar() {
           },
         ],
       },
+      {
+        name: "Activation",
+        path: "/activation",
+        icon: <KeyRound className="h-5 w-5 text-amber-500" />,
+        adminOnly: true,
+      },
       {
         name: "Database Management",
         path: "/database-management",