refactor: remove security-related hooks and pages

- Deleted `useSecurity.ts` hook which managed authentication users, providers, and policies.
- Removed `Policies.tsx`, `Providers.tsx`, and `Users.tsx` pages that utilized the above hook.
- Cleaned up the `index.tsx` file in the Security section to remove references to the deleted pages.
- Updated mock data by removing unused properties related to forward authentication.

frontend/src/api/proxyHosts.ts

@@ -30,9 +30,6 @@ export interface ProxyHost {
   hsts_subdomains: boolean;
   block_exploits: boolean;
   websocket_support: boolean;
-  forward_auth_enabled: boolean;
-  forward_auth_bypass: string;
-  auth_policy_id?: number | null;
   locations: Location[];
   advanced_config?: string;
   enabled: boolean;