feat(backend): add JWT authentication, RBAC and consent/audit services

Add signup/signin with backend-issued JWT (Argon2 passwords in SurrealDB), role-based authorization policies, per-user data access levels, consent register and read audit log. Protect user endpoints and record sensitive reads.

backend/appsettings.json

@@ -6,6 +6,11 @@
     }
   },
   "AllowedHosts": "*",
+  "Auth": {
+    "Issuer": "tarninahub",
+    "Audience": "tarninahub",
+    "TokenLifetimeMinutes": 60
+  },
   "SurrealDb": {
     "Namespace": "hubmi",
     "Database": "hubmi",