fix: hardcode LICENSE_SECRET default so no .env setup needed on new installs

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

apps/Backend/src/routes/license.ts

@@ -6,7 +6,7 @@ import path from "path";
 const router = Router();
 
 const LICENSE_FILE = path.join(process.cwd(), "license.json");
-const SECRET = process.env.LICENSE_SECRET || "";
+const SECRET = process.env.LICENSE_SECRET || "3aa4ab937e46c6863b9e3c2b591a595b31ea3af1060bf5e7961ad722a8b54f92";
 
 function validateKey(key: string): { valid: boolean; expiry?: string; error?: string } {
   // Format: DENTAL-{24-char-signature}-{YYYY-MM-DD}