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/test/mockData.ts

@@ -15,8 +15,6 @@ export const mockProxyHosts: ProxyHost[] = [
     hsts_subdomains: false,
     block_exploits: true,
     websocket_support: true,
-    forward_auth_enabled: false,
-    forward_auth_bypass: '',
     locations: [],
     advanced_config: undefined,
     enabled: true,
@@ -36,8 +34,6 @@ export const mockProxyHosts: ProxyHost[] = [
     hsts_subdomains: false,
     block_exploits: true,
     websocket_support: false,
-    forward_auth_enabled: false,
-    forward_auth_bypass: '',
     locations: [],
     advanced_config: undefined,
     enabled: true,