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/Backend/.env

@@ -1,6 +1,7 @@
 NODE_ENV="development"
 HOST=0.0.0.0
 PORT=5000
+CLOUDFLARE_HOST=communitydentistsoflowell.mydentalofficemanagement.com
 FRONTEND_URLS=http://localhost:3000,http://communitydentistsoflowell.mydentalofficemanagement.com,https://communitydentistsoflowell.mydentalofficemanagement.com
 SELENIUM_AGENT_BASE_URL=http://localhost:5002
 JWT_SECRET = 'dentalsecret'
@@ -8,4 +9,5 @@ DB_HOST=localhost
 DB_USER=postgres
 DB_PASSWORD=mypassword
 DB_NAME=dentalapp
-DATABASE_URL=postgresql://postgres:mypassword@localhost:5432/dentalapp
+DATABASE_URL=postgresql://postgres:mypassword@localhost:5432/dentalapp
+LICENSE_SECRET=3aa4ab937e46c6863b9e3c2b591a595b31ea3af1060bf5e7961ad722a8b54f92